Cleanup media::KeySystemSupportObserver

- Rename KeySystemSupportObserver to KeySystemSupportRegistration
- Remove unnecessary virtual function
- Add clarifying comments.

TESTED:
* Add logs to see the size observer remote set in browser process.
  (after this line
  https://source.chromium.org/chromium/chromium/src/+/main:content/browser/media/key_system_support_impl.cc;drc=eb3c1d87f1c717de44fdaadb8b83041584f6a6b3;l=59)

The following is observed only when moving key systems to a per-frame
model. See
https://chromium-review.googlesource.com/c/chromium/src/+/5168850

* Visit integration.widevine.com/player
* Click play observer logs (observer_remotes_.size() = 1)
* Visit another site (e.g. shaka-player-demo.appspot.com) and play
  encrypted media
* Check logs find (observer_remotes_.size() = 2)
* Close integration.widevine.com/player tab and ensure render process
  for that tab is destroyed (e.g. in Task Manager)
* Visit integration.staging.widevine.com/player and click play
* Observer logs and find (observer_remotes_.size() = 2) whereas before
  https://chromium-review.googlesource.com/c/chromium/src/+/5168850 the
  logs would say (observer_remotes_.size() = 3)

Bug: b/321307544
Change-Id: I78133a594c0fcf96326ce25aa42fbe754491bc60
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5381159
Commit-Queue: Feras Aldahlawi <feras@chromium.org>
Reviewed-by: Xiaohan Wang <xhwang@chromium.org>
Reviewed-by: Peter Beverloo <peter@chromium.org>
Reviewed-by: Nasko Oskov <nasko@chromium.org>
Reviewed-by: Zijie He <zijiehe@google.com>
Reviewed-by: Sean Topping <seantopping@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1275988}

android_webview/renderer/aw_content_renderer_client.cc

@@ -235,7 +235,7 @@ void AwContentRendererClient::RunScriptsAtDocumentStart(
   communication->RunScriptsAtDocumentStart();
 }
 
-std::unique_ptr<media::KeySystemSupportObserver>
+std::unique_ptr<media::KeySystemSupportRegistration>
 AwContentRendererClient::GetSupportedKeySystems(
     media::GetSupportedKeySystemsCB cb) {
   // WebView always allows persisting data.

android_webview/renderer/aw_content_renderer_client.h

@@ -55,7 +55,7 @@ class AwContentRendererClient : public content::ContentRendererClient,
   uint64_t VisitedLinkHash(std::string_view canonical_url) override;
   bool IsLinkVisited(uint64_t link_hash) override;
   void RunScriptsAtDocumentStart(content::RenderFrame* render_frame) override;
-  std::unique_ptr<media::KeySystemSupportObserver> GetSupportedKeySystems(
+  std::unique_ptr<media::KeySystemSupportRegistration> GetSupportedKeySystems(
       media::GetSupportedKeySystemsCB cb) override;
   std::unique_ptr<blink::WebSocketHandshakeThrottleProvider>
   CreateWebSocketHandshakeThrottleProvider() override;

chrome/renderer/chrome_content_renderer_client.cc

@@ -1591,7 +1591,7 @@ ChromeContentRendererClient::CreateWebSocketHandshakeThrottleProvider() {
       browser_interface_broker_.get());
 }
 
-std::unique_ptr<media::KeySystemSupportObserver>
+std::unique_ptr<media::KeySystemSupportRegistration>
 ChromeContentRendererClient::GetSupportedKeySystems(
     media::GetSupportedKeySystemsCB cb) {
 #if BUILDFLAG(ENABLE_LIBRARY_CDMS) || BUILDFLAG(IS_WIN) || BUILDFLAG(IS_ANDROID)

chrome/renderer/chrome_content_renderer_client.h

@@ -27,7 +27,7 @@
 #include "content/public/renderer/render_thread.h"
 #include "extensions/buildflags/buildflags.h"
 #include "ipc/ipc_channel_proxy.h"
-#include "media/base/key_systems_support_observer.h"
+#include "media/base/key_systems_support_registration.h"
 #include "media/media_buildflags.h"
 #include "mojo/public/cpp/bindings/associated_remote.h"
 #include "mojo/public/cpp/bindings/generic_pending_receiver.h"
@@ -171,7 +171,7 @@ class ChromeContentRendererClient
   std::unique_ptr<media::SpeechRecognitionClient> CreateSpeechRecognitionClient(
       content::RenderFrame* render_frame) override;
 #endif  // BUILDFLAG(ENABLE_SPEECH_SERVICE)
-  std::unique_ptr<media::KeySystemSupportObserver> GetSupportedKeySystems(
+  std::unique_ptr<media::KeySystemSupportRegistration> GetSupportedKeySystems(
       media::GetSupportedKeySystemsCB cb) override;
   bool IsPluginAllowedToUseCameraDeviceAPI(const GURL& url) override;
   void RunScriptsAtDocumentStart(content::RenderFrame* render_frame) override;

chrome/renderer/media/chrome_key_systems.cc

@@ -6,9 +6,9 @@
 
 #include "chrome/renderer/chrome_render_thread_observer.h"
 #include "components/cdm/renderer/key_system_support_update.h"
-#include "media/base/key_systems_support_observer.h"
+#include "media/base/key_systems_support_registration.h"
 
-std::unique_ptr<media::KeySystemSupportObserver> GetChromeKeySystems(
+std::unique_ptr<media::KeySystemSupportRegistration> GetChromeKeySystems(
     media::GetSupportedKeySystemsCB cb) {
   return cdm::GetSupportedKeySystemsUpdates(
       !ChromeRenderThreadObserver::is_incognito_process(), std::move(cb));

chrome/renderer/media/chrome_key_systems.h

@@ -6,10 +6,10 @@
 #define CHROME_RENDERER_MEDIA_CHROME_KEY_SYSTEMS_H_
 
 #include "media/base/key_system_info.h"
-#include "media/base/key_systems_support_observer.h"
+#include "media/base/key_systems_support_registration.h"
 
 // Register the key systems supported by the chrome/ layer.
-std::unique_ptr<media::KeySystemSupportObserver> GetChromeKeySystems(
+std::unique_ptr<media::KeySystemSupportRegistration> GetChromeKeySystems(
     media::GetSupportedKeySystemsCB cb);
 
 #endif  // CHROME_RENDERER_MEDIA_CHROME_KEY_SYSTEMS_H_

chromecast/renderer/cast_content_renderer_client.cc

@@ -170,7 +170,7 @@ void CastContentRendererClient::RunScriptsAtDocumentStart(
 void CastContentRendererClient::RunScriptsAtDocumentEnd(
     content::RenderFrame* render_frame) {}
 
-std::unique_ptr<::media::KeySystemSupportObserver>
+std::unique_ptr<::media::KeySystemSupportRegistration>
 CastContentRendererClient::GetSupportedKeySystems(
     ::media::GetSupportedKeySystemsCB cb) {
 #if BUILDFLAG(IS_ANDROID)

chromecast/renderer/cast_content_renderer_client.h

@@ -17,7 +17,7 @@
 #include "content/public/renderer/content_renderer_client.h"
 #include "media/base/audio_codecs.h"
 #include "media/base/audio_parameters.h"
-#include "media/base/key_systems_support_observer.h"
+#include "media/base/key_systems_support_registration.h"
 #include "mojo/public/cpp/bindings/receiver.h"
 
 namespace cast_receiver {
@@ -56,7 +56,7 @@ class CastContentRendererClient
   void RenderFrameCreated(content::RenderFrame* render_frame) override;
   void RunScriptsAtDocumentStart(content::RenderFrame* render_frame) override;
   void RunScriptsAtDocumentEnd(content::RenderFrame* render_frame) override;
-  std::unique_ptr<::media::KeySystemSupportObserver> GetSupportedKeySystems(
+  std::unique_ptr<::media::KeySystemSupportRegistration> GetSupportedKeySystems(
       ::media::GetSupportedKeySystemsCB cb) override;
   bool IsSupportedAudioType(const ::media::AudioType& type) override;
   bool IsSupportedVideoType(const ::media::VideoType& type) override;

components/cdm/renderer/key_system_support_update.cc

@@ -589,9 +589,9 @@ void OnKeySystemSupportUpdated(
 
 }  // namespace
 
-std::unique_ptr<media::KeySystemSupportObserver> GetSupportedKeySystemsUpdates(
-    bool can_persist_data,
-    media::GetSupportedKeySystemsCB cb) {
+std::unique_ptr<media::KeySystemSupportRegistration>
+GetSupportedKeySystemsUpdates(bool can_persist_data,
+                              media::GetSupportedKeySystemsCB cb) {
   return content::ObserveKeySystemSupportUpdate(base::BindRepeating(
       &OnKeySystemSupportUpdated, can_persist_data, std::move(cb)));
 }

components/cdm/renderer/key_system_support_update.h

@@ -6,7 +6,7 @@
 #define COMPONENTS_CDM_RENDERER_KEY_SYSTEM_SUPPORT_UPDATE_H_
 
 #include "media/base/key_system_info.h"
-#include "media/base/key_systems_support_observer.h"
+#include "media/base/key_systems_support_registration.h"
 
 namespace cdm {
 
@@ -15,9 +15,9 @@ namespace cdm {
 // incognito mode). `cb` is called with the list of available key systems, and
 // may be called multiple times if the list changes (e.g. a new key system
 // becomes available).
-std::unique_ptr<media::KeySystemSupportObserver> GetSupportedKeySystemsUpdates(
-    bool can_persist_data,
-    media::GetSupportedKeySystemsCB cb);
+std::unique_ptr<media::KeySystemSupportRegistration>
+GetSupportedKeySystemsUpdates(bool can_persist_data,
+                              media::GetSupportedKeySystemsCB cb);
 
 }  // namespace cdm
 

content/public/renderer/content_renderer_client.cc

@@ -167,7 +167,7 @@ bool ContentRendererClient::IsOriginIsolatedPepperPlugin(
   return true;
 }
 
-std::unique_ptr<media::KeySystemSupportObserver>
+std::unique_ptr<media::KeySystemSupportRegistration>
 ContentRendererClient::GetSupportedKeySystems(
     media::GetSupportedKeySystemsCB cb) {
   std::move(cb).Run({});

content/public/renderer/content_renderer_client.h

@@ -26,7 +26,7 @@
 #include "content/public/common/content_client.h"
 #include "media/base/audio_parameters.h"
 #include "media/base/key_system_info.h"
-#include "media/base/key_systems_support_observer.h"
+#include "media/base/key_systems_support_registration.h"
 #include "media/base/supported_types.h"
 #include "third_party/blink/public/platform/url_loader_throttle_provider.h"
 #include "third_party/blink/public/platform/web_content_settings_client.h"
@@ -282,7 +282,7 @@ class CONTENT_EXPORT ContentRendererClient {
   virtual bool IsOriginIsolatedPepperPlugin(const base::FilePath& plugin_path);
 
   // Allows embedder to register the key system(s) it supports.
-  virtual std::unique_ptr<media::KeySystemSupportObserver>
+  virtual std::unique_ptr<media::KeySystemSupportRegistration>
   GetSupportedKeySystems(media::GetSupportedKeySystemsCB cb);
 
   // Allows embedder to describe customized audio capabilities.

content/public/renderer/key_system_support.cc

@@ -6,14 +6,16 @@
 
 #include "base/logging.h"
 #include "content/public/renderer/render_thread.h"
-#include "media/base/key_systems_support_observer.h"
+#include "media/base/key_systems_support_registration.h"
 #include "mojo/public/cpp/bindings/remote.h"
 #include "mojo/public/cpp/bindings/self_owned_receiver.h"
 
 namespace content {
 
+namespace {
+
 class KeySystemSupportObserverImpl
-    : public media::KeySystemSupportObserver,
+    : public media::KeySystemSupportRegistration,
       public media::mojom::KeySystemSupportObserver {
  public:
   KeySystemSupportObserverImpl(
@@ -38,24 +40,26 @@ class KeySystemSupportObserverImpl
   mojo::Receiver<media::mojom::KeySystemSupportObserver> receiver_;
 };
 
-std::unique_ptr<media::KeySystemSupportObserver> ObserveKeySystemSupportUpdate(
-    media::KeySystemSupportCB cb) {
+}  // namespace
+
+std::unique_ptr<media::KeySystemSupportRegistration>
+ObserveKeySystemSupportUpdate(media::KeySystemSupportCB cb) {
   DVLOG(1) << __func__;
 
-  // `key_system_support` will be destructed after this function returns. This
-  // is fine since the observer will stay registered in KeySystemSupportImpl,
-  // which is a singleton in the browser process.
+  // `key_system_support` will stay alive as long as the returned value of this
+  // function is not destructed by the caller.
   mojo::Remote<media::mojom::KeySystemSupport> key_system_support;
   content::RenderThread::Get()->BindHostReceiver(
       key_system_support.BindNewPipeAndPassReceiver());
 
   mojo::PendingRemote<media::mojom::KeySystemSupportObserver> observer_remote;
-  auto key_system_support_update =
-      std::make_unique<KeySystemSupportObserverImpl>(
-          std::move(cb), observer_remote.InitWithNewPipeAndPassReceiver());
+  std::unique_ptr<media::KeySystemSupportRegistration>
+      key_system_support_registration =
+          std::make_unique<KeySystemSupportObserverImpl>(
+              std::move(cb), observer_remote.InitWithNewPipeAndPassReceiver());
   key_system_support->AddObserver(std::move(observer_remote));
 
-  return std::move(key_system_support_update);
+  return key_system_support_registration;
 }
 
 }  // namespace content

content/public/renderer/key_system_support.h

@@ -11,7 +11,7 @@
 #include "base/functional/callback.h"
 #include "content/common/content_export.h"
 #include "media/base/key_system_capability.h"
-#include "media/base/key_systems_support_observer.h"
+#include "media/base/key_systems_support_registration.h"
 #include "media/mojo/mojom/key_system_support.mojom.h"
 
 namespace content {
@@ -23,7 +23,7 @@ using KeySystemSupportCB = base::RepeatingCallback<void(KeySystemCapabilities)>;
 // Observes key system support updates. The callback `cb` will be called with
 // the current key system support, then called every time the key system support
 // changes.
-CONTENT_EXPORT std::unique_ptr<media::KeySystemSupportObserver>
+CONTENT_EXPORT std::unique_ptr<media::KeySystemSupportRegistration>
 ObserveKeySystemSupportUpdate(media::KeySystemSupportCB cb);
 
 }  // namespace content

content/renderer/media/render_media_client.cc

@@ -76,7 +76,7 @@ RenderMediaClient::RenderMediaClient()
 
 RenderMediaClient::~RenderMediaClient() = default;
 
-std::unique_ptr<media::KeySystemSupportObserver>
+std::unique_ptr<media::KeySystemSupportRegistration>
 RenderMediaClient::GetSupportedKeySystems(media::GetSupportedKeySystemsCB cb) {
   return GetContentClient()->renderer()->GetSupportedKeySystems(std::move(cb));
 }

content/renderer/media/render_media_client.h

@@ -8,7 +8,7 @@
 #include "base/synchronization/waitable_event.h"
 #include "media/base/audio_parameters.h"
 #include "media/base/decoder.h"
-#include "media/base/key_systems_support_observer.h"
+#include "media/base/key_systems_support_registration.h"
 #include "media/base/media_client.h"
 #include "media/base/supported_video_decoder_config.h"
 #include "media/mojo/mojom/interface_factory.mojom.h"
@@ -30,7 +30,7 @@ class RenderMediaClient : public media::MediaClient {
   static void Initialize();
 
   // MediaClient implementation.
-  std::unique_ptr<media::KeySystemSupportObserver> GetSupportedKeySystems(
+  std::unique_ptr<media::KeySystemSupportRegistration> GetSupportedKeySystems(
       media::GetSupportedKeySystemsCB cb) final;
   bool IsSupportedAudioType(const media::AudioType& type) final;
   bool IsSupportedVideoType(const media::VideoType& type) final;

content/shell/renderer/shell_content_renderer_client.cc

@@ -297,7 +297,7 @@ ShellContentRendererClient::CreateURLLoaderThrottleProvider(
 }
 
 #if BUILDFLAG(ENABLE_MOJO_CDM)
-std::unique_ptr<media::KeySystemSupportObserver>
+std::unique_ptr<media::KeySystemSupportRegistration>
 ShellContentRendererClient::GetSupportedKeySystems(
     media::GetSupportedKeySystemsCB cb) {
   media::KeySystemInfos key_systems;

content/shell/renderer/shell_content_renderer_client.h

@@ -56,7 +56,7 @@ class ShellContentRendererClient : public ContentRendererClient {
       blink::URLLoaderThrottleProviderType provider_type) override;
 
 #if BUILDFLAG(ENABLE_MOJO_CDM)
-  std::unique_ptr<media::KeySystemSupportObserver> GetSupportedKeySystems(
+  std::unique_ptr<media::KeySystemSupportRegistration> GetSupportedKeySystems(
       media::GetSupportedKeySystemsCB cb) override;
 #endif
 

fuchsia_web/webengine/renderer/web_engine_content_renderer_client.cc

@@ -200,7 +200,7 @@ WebEngineContentRendererClient::CreateURLLoaderThrottleProvider(
   return std::make_unique<WebEngineURLLoaderThrottleProvider>(this);
 }
 
-std::unique_ptr<media::KeySystemSupportObserver>
+std::unique_ptr<media::KeySystemSupportRegistration>
 WebEngineContentRendererClient::GetSupportedKeySystems(
     media::GetSupportedKeySystemsCB cb) {
   media::KeySystemInfos key_systems;

fuchsia_web/webengine/renderer/web_engine_content_renderer_client.h

@@ -51,7 +51,7 @@ class WebEngineContentRendererClient : public content::ContentRendererClient {
   // content::ContentRendererClient overrides.
   void RenderThreadStarted() override;
   void RenderFrameCreated(content::RenderFrame* render_frame) override;
-  std::unique_ptr<media::KeySystemSupportObserver> GetSupportedKeySystems(
+  std::unique_ptr<media::KeySystemSupportRegistration> GetSupportedKeySystems(
       media::GetSupportedKeySystemsCB cb) override;
   bool IsSupportedVideoType(const media::VideoType& type) override;
   std::unique_ptr<blink::URLLoaderThrottleProvider>

media/base/BUILD.gn

@@ -198,8 +198,8 @@ source_set("base") {
     "key_systems.h",
     "key_systems_impl.cc",
     "key_systems_impl.h",
-    "key_systems_support_observer.cc",
-    "key_systems_support_observer.h",
+    "key_systems_support_registration.cc",
+    "key_systems_support_registration.h",
     "localized_strings.cc",
     "localized_strings.h",
     "logging_override_if_enabled.h",

media/base/key_systems_impl.cc

@@ -309,7 +309,7 @@ void KeySystemsImpl::UpdateSupportedKeySystems() {
     OnSupportedKeySystemsUpdated({});
     return;
   }
-  key_system_support_observer_ = GetMediaClient()->GetSupportedKeySystems(
+  key_system_support_registration_ = GetMediaClient()->GetSupportedKeySystems(
       base::BindRepeating(&KeySystemsImpl::OnSupportedKeySystemsUpdated,
                           weak_factory_.GetWeakPtr()));
 }

media/base/key_systems_impl.h

@@ -20,7 +20,7 @@
 #include "media/base/eme_constants.h"
 #include "media/base/key_system_info.h"
 #include "media/base/key_systems.h"
-#include "media/base/key_systems_support_observer.h"
+#include "media/base/key_systems_support_registration.h"
 #include "media/base/media_export.h"
 
 namespace media {
@@ -128,7 +128,8 @@ class KeySystemsImpl : public KeySystems {
   // Makes sure all methods are called from the same thread.
   base::ThreadChecker thread_checker_;
 
-  std::unique_ptr<KeySystemSupportObserver> key_system_support_observer_;
+  std::unique_ptr<KeySystemSupportRegistration>
+      key_system_support_registration_;
 
   base::WeakPtrFactory<KeySystemsImpl> weak_factory_{this};
 };

media/base/key_systems_support_observer.cc

@@ -1,12 +0,0 @@
-// Copyright 2024 The Chromium Authors
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include "media/base/key_systems_support_observer.h"
-
-namespace media {
-
-KeySystemSupportObserver::KeySystemSupportObserver() = default;
-KeySystemSupportObserver::~KeySystemSupportObserver() = default;
-
-}  // namespace media

media/base/key_systems_support_observer.h

@@ -1,32 +0,0 @@
-// Copyright 2024 The Chromium Authors
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef MEDIA_BASE_KEY_SYSTEMS_SUPPORT_OBSERVER_H_
-#define MEDIA_BASE_KEY_SYSTEMS_SUPPORT_OBSERVER_H_
-
-#include "base/containers/flat_map.h"
-#include "base/functional/callback.h"
-#include "media/base/key_system_capability.h"
-#include "media/base/media_export.h"
-
-namespace media {
-
-using KeySystemCapabilities =
-    base::flat_map<std::string, media::KeySystemCapability>;
-using KeySystemSupportCB = base::RepeatingCallback<void(KeySystemCapabilities)>;
-
-class MEDIA_EXPORT KeySystemSupportObserver {
- public:
-  KeySystemSupportObserver();
-  KeySystemSupportObserver(const KeySystemSupportObserver&) = delete;
-  KeySystemSupportObserver& operator=(const KeySystemSupportObserver&) = delete;
-  virtual ~KeySystemSupportObserver();
-
-  virtual void OnKeySystemSupportUpdated(
-      const KeySystemCapabilities& key_system_capabilities) = 0;
-};
-
-}  // namespace media
-
-#endif  // MEDIA_BASE_KEY_SYSTEMS_SUPPORT_OBSERVER_H_

media/base/key_systems_support_registration.cc

@@ -0,0 +1,12 @@
+// Copyright 2024 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "media/base/key_systems_support_registration.h"
+
+namespace media {
+
+KeySystemSupportRegistration::KeySystemSupportRegistration() = default;
+KeySystemSupportRegistration::~KeySystemSupportRegistration() = default;
+
+}  // namespace media

media/base/key_systems_support_registration.h

@@ -0,0 +1,33 @@
+// Copyright 2024 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef MEDIA_BASE_KEY_SYSTEMS_SUPPORT_REGISTRATION_H_
+#define MEDIA_BASE_KEY_SYSTEMS_SUPPORT_REGISTRATION_H_
+
+#include "base/containers/flat_map.h"
+#include "base/functional/callback.h"
+#include "media/base/key_system_capability.h"
+#include "media/base/media_export.h"
+
+namespace media {
+
+using KeySystemCapabilities =
+    base::flat_map<std::string, media::KeySystemCapability>;
+using KeySystemSupportCB = base::RepeatingCallback<void(KeySystemCapabilities)>;
+
+// A class that is used to keep the KeySystemSupport and
+// KeySystemSupportObserver mojo channel registered between renderer and
+// browser alive and destructed properly.
+class MEDIA_EXPORT KeySystemSupportRegistration {
+ public:
+  KeySystemSupportRegistration();
+  KeySystemSupportRegistration(const KeySystemSupportRegistration&) = delete;
+  KeySystemSupportRegistration& operator=(const KeySystemSupportRegistration&) =
+      delete;
+  virtual ~KeySystemSupportRegistration();
+};
+
+}  // namespace media
+
+#endif  // MEDIA_BASE_KEY_SYSTEMS_SUPPORT_REGISTRATION_H_

media/base/key_systems_unittest.cc

@@ -234,7 +234,7 @@ class TestMediaClient : public MediaClient {
   ~TestMediaClient() override;
 
   // MediaClient implementation.
-  std::unique_ptr<::media::KeySystemSupportObserver> GetSupportedKeySystems(
+  std::unique_ptr<::media::KeySystemSupportRegistration> GetSupportedKeySystems(
       GetSupportedKeySystemsCB cb) final;
   bool IsSupportedAudioType(const AudioType& type) final;
   bool IsSupportedVideoType(const VideoType& type) final;
@@ -257,7 +257,7 @@ class TestMediaClient : public MediaClient {
 TestMediaClient::TestMediaClient() = default;
 TestMediaClient::~TestMediaClient() = default;
 
-std::unique_ptr<::media::KeySystemSupportObserver>
+std::unique_ptr<::media::KeySystemSupportRegistration>
 TestMediaClient::GetSupportedKeySystems(GetSupportedKeySystemsCB cb) {
   // Save the callback for future updates.
   get_supported_key_systems_cb_ = cb;

media/base/media_client.h

@@ -12,7 +12,7 @@
 #include "media/base/audio_codecs.h"
 #include "media/base/audio_parameters.h"
 #include "media/base/key_system_info.h"
-#include "media/base/key_systems_support_observer.h"
+#include "media/base/key_systems_support_registration.h"
 #include "media/base/media_export.h"
 #include "media/base/media_types.h"
 #include "media/base/video_codecs.h"
@@ -42,7 +42,7 @@ class MEDIA_EXPORT MediaClient {
   virtual ~MediaClient();
 
   // Adds properties for supported key systems.
-  virtual std::unique_ptr<media::KeySystemSupportObserver>
+  virtual std::unique_ptr<media::KeySystemSupportRegistration>
   GetSupportedKeySystems(GetSupportedKeySystemsCB cb) = 0;
 
   // Returns true if the given audio config is supported.

media/base/mock_filters.h

@@ -872,7 +872,7 @@ class MockMediaClient : public media::MediaClient {
 
   // MediaClient implementation.
   MOCK_METHOD1(GetSupportedKeySystems,
-               std::unique_ptr<::media::KeySystemSupportObserver>(
+               std::unique_ptr<::media::KeySystemSupportRegistration>(
                    GetSupportedKeySystemsCB cb));
   MOCK_METHOD1(IsSupportedAudioType, bool(const media::AudioType& type));
   MOCK_METHOD1(IsSupportedVideoType, bool(const media::VideoType& type));