[Background Fetch] Add a kill switch feature flag.

Tested by starting up chrome with --disable-features=BackgroundFetch

Change-Id: I8a1c3de3f7763b51f5384492f28e8afb3e3d9991
Reviewed-on: https://chromium-review.googlesource.com/1240299
Reviewed-by: Peter Beverloo <peter@chromium.org>
Reviewed-by: Tobias Sargeant <tobiasjs@chromium.org>
Reviewed-by: Mugdha Lakhani <nator@chromium.org>
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Commit-Queue: Rayan Kanso <rayankans@chromium.org>
Cr-Commit-Position: refs/heads/master@{#593922}

android_webview/lib/aw_main_delegate.cc

@@ -118,9 +118,6 @@ bool AwMainDelegate::BasicStartupComplete(int* exit_code) {
   // metadata and controls.
   cl->AppendSwitch(switches::kDisableMediaSessionAPI);
 
-  // Background Fetch is not supported.
-  cl->AppendSwitch(switches::kDisableBackgroundFetch);
-
 #if defined(V8_USE_EXTERNAL_STARTUP_DATA)
   if (cl->GetSwitchValueASCII(switches::kProcessType).empty()) {
     // Browser process (no type specified).
@@ -192,6 +189,8 @@ bool AwMainDelegate::BasicStartupComplete(int* exit_code) {
       *cl, autofill::features::kAutofillRestrictUnownedFieldsToFormlessCheckout
                .name);
 
+  CommandLineHelper::AddDisabledFeature(*cl, features::kBackgroundFetch.name);
+
   android_webview::RegisterPathProvider();
 
   safe_browsing_api_handler_.reset(

content/browser/renderer_host/render_process_host_impl.cc

@@ -2946,7 +2946,6 @@ void RenderProcessHostImpl::PropagateBrowserCommandLineToRenderer(
     switches::kDisable2dCanvasImageChromium,
     switches::kDisableAcceleratedJpegDecoding,
     switches::kDisableAcceleratedVideoDecode,
-    switches::kDisableBackgroundFetch,
     switches::kDisableBackgroundTasks,
     switches::kDisableBackgroundTimerThrottling,
     switches::kDisableBreakpad,

content/child/runtime_features.cc

@@ -500,7 +500,7 @@ void SetRuntimeFeaturesDefaultsAndUpdateFromArgs(
   WebRuntimeFeatures::EnablePortals(
       base::FeatureList::IsEnabled(blink::features::kPortals));
 
-  if (command_line.HasSwitch(switches::kDisableBackgroundFetch))
+  if (!base::FeatureList::IsEnabled(features::kBackgroundFetch))
     WebRuntimeFeatures::EnableBackgroundFetch(false);
 
   WebRuntimeFeatures::EnableNoHoverAfterLayoutChange(

content/public/common/content_features.cc

@@ -50,6 +50,10 @@ const base::Feature kAudioServiceLaunchOnStartup{
 const base::Feature kAudioServiceOutOfProcess{
     "AudioServiceOutOfProcess", base::FEATURE_DISABLED_BY_DEFAULT};
 
+// Kill switch for Background Fetch.
+const base::Feature kBackgroundFetch{"BackgroundFetch",
+                                     base::FEATURE_ENABLED_BY_DEFAULT};
+
 // Enable incremental marking for Blink's heap managed by the Oilpan garbage
 // collector.
 const base::Feature kBlinkHeapIncrementalMarking{

content/public/common/content_features.h

@@ -25,6 +25,7 @@ CONTENT_EXPORT extern const base::Feature kAsmJsToWebAssembly;
 CONTENT_EXPORT extern const base::Feature kAudioServiceAudioStreams;
 CONTENT_EXPORT extern const base::Feature kAudioServiceLaunchOnStartup;
 CONTENT_EXPORT extern const base::Feature kAudioServiceOutOfProcess;
+CONTENT_EXPORT extern const base::Feature kBackgroundFetch;
 CONTENT_EXPORT extern const base::Feature kBlinkHeapIncrementalMarking;
 CONTENT_EXPORT extern const base::Feature kBloatedRendererDetection;
 CONTENT_EXPORT extern const base::Feature kBlockCredentialedSubresources;

content/public/common/content_switches.cc

@@ -86,9 +86,6 @@ const char kDisableBackingStoreLimit[]      = "disable-backing-store-limit";
 const char kDisableBackgroundingOccludedWindowsForTesting[] =
     "disable-backgrounding-occluded-windows";
 
-// Disable Background Fetch.
-const char kDisableBackgroundFetch[] = "disable-background-fetch";
-
 // Disable task throttling of timer tasks from background pages.
 const char kDisableBackgroundTimerThrottling[] =
     "disable-background-timer-throttling";

content/public/common/content_switches.h

@@ -38,7 +38,6 @@ CONTENT_EXPORT extern const char kDisableAudioSupportForDesktopShare[];
 extern const char kDisableBackingStoreLimit[];
 CONTENT_EXPORT extern const char
     kDisableBackgroundingOccludedWindowsForTesting[];
-CONTENT_EXPORT extern const char kDisableBackgroundFetch[];
 CONTENT_EXPORT extern const char kDisableBackgroundTimerThrottling[];
 CONTENT_EXPORT extern const char kDisableBlinkFeatures[];
 CONTENT_EXPORT extern const char kDisableCompositorUkmForTests[];