[FastPair] Add Mediator to ash/shell

This changes adds quick_pair::Mediator to //ash/shell. This class is
the entry point for the Quick Pair system which enables Fast Pair.

Fixed: 1227437
Change-Id: Ia9b7e32d8df2efb5524ac86ff607bec7d77aa200
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3011114
Commit-Queue: Shane Fitzpatrick <shanefitz@google.com>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#899773}

ash/BUILD.gn

@@ -1842,6 +1842,7 @@ component("ash") {
     "//ash/login/resources:resources_grit",
     "//ash/public/cpp/ambient/proto",
     "//ash/quick_pair",
+    "//ash/quick_pair/keyed_service",
     "//ash/services/recording",
     "//ash/services/recording/public/mojom",
     "//ash/system/machine_learning:user_settings_event_proto",

ash/quick_pair/keyed_service/quick_pair_mediator.cc

@@ -9,10 +9,33 @@
 #include "ash/quick_pair/common/device.h"
 #include "ash/quick_pair/common/logging.h"
 #include "ash/quick_pair/feature_status_tracker/quick_pair_feature_status_tracker.h"
+#include "ash/quick_pair/feature_status_tracker/quick_pair_feature_status_tracker_impl.h"
+#include "ash/quick_pair/scanning/scanner_broker_impl.h"
 
 namespace ash {
 namespace quick_pair {
 
+namespace {
+
+Mediator::Factory* g_test_factory = nullptr;
+
+}
+
+// static
+std::unique_ptr<Mediator> Mediator::Factory::Create() {
+  if (g_test_factory)
+    return g_test_factory->BuildInstance();
+
+  return std::make_unique<Mediator>(
+      std::make_unique<FeatureStatusTrackerImpl>(),
+      std::make_unique<ScannerBrokerImpl>());
+}
+
+// static
+void Mediator::Factory::SetFactoryForTesting(Factory* factory) {
+  g_test_factory = factory;
+}
+
 Mediator::Mediator(std::unique_ptr<FeatureStatusTracker> feature_status_tracker,
                    std::unique_ptr<ScannerBroker> scanner_broker)
     : feature_status_tracker_(std::move(feature_status_tracker)),

ash/quick_pair/keyed_service/quick_pair_mediator.h

@@ -20,6 +20,16 @@ namespace quick_pair {
 class Mediator : public FeatureStatusTracker::Observer,
                  public ScannerBroker::Observer {
  public:
+  class Factory {
+   public:
+    static std::unique_ptr<Mediator> Create();
+    static void SetFactoryForTesting(Factory* factory);
+    virtual ~Factory() = default;
+
+   private:
+    virtual std::unique_ptr<Mediator> BuildInstance() = 0;
+  };
+
   Mediator(std::unique_ptr<FeatureStatusTracker> feature_status_tracker,
            std::unique_ptr<ScannerBroker> scanner_broker);
   Mediator(const Mediator&) = delete;

ash/shell.cc

@@ -87,6 +87,7 @@
 #include "ash/public/cpp/shell_window_ids.h"
 #include "ash/public/cpp/views_text_services_context_menu_impl.h"
 #include "ash/quick_answers/quick_answers_controller_impl.h"
+#include "ash/quick_pair/keyed_service/quick_pair_mediator.h"
 #include "ash/root_window_controller.h"
 #include "ash/screenshot_delegate.h"
 #include "ash/session/session_controller_impl.h"
@@ -559,7 +560,8 @@ Shell::Shell(std::unique_ptr<ShellDelegate> shell_delegate)
       shell_delegate_(std::move(shell_delegate)),
       shutdown_controller_(std::make_unique<ShutdownControllerImpl>()),
       system_tray_notifier_(std::make_unique<SystemTrayNotifier>()),
-      native_cursor_manager_(nullptr) {
+      native_cursor_manager_(nullptr),
+      quick_pair_mediator_(quick_pair::Mediator::Factory::Create()) {
   AccelerometerReader::GetInstance()->Initialize();
 
   login_screen_controller_ =

ash/shell.h

@@ -207,6 +207,10 @@ class ArcInputMethodBoundsTracker;
 
 enum class LoginStatus;
 
+namespace quick_pair {
+class Mediator;
+}  // namespace quick_pair
+
 // Shell is a singleton object that presents the Shell API and implements the
 // RootWindow's delegate interface.
 //
@@ -889,6 +893,8 @@ class ASH_EXPORT Shell : public SessionObserver,
 
   std::unique_ptr<OcclusionTrackerPauser> occlusion_tracker_pauser_;
 
+  std::unique_ptr<quick_pair::Mediator> quick_pair_mediator_;
+
   base::ObserverList<ShellObserver>::Unchecked shell_observers_;
 
   base::WeakPtrFactory<Shell> weak_factory_{this};