Unflag the MediaDevices devicechange event in Blink.

The feature is still disabled on Android because SystemMonitor is not
yet supported on that platform.

Intent to ship: https://groups.google.com/a/chromium.org/forum/#!topic/blink-dev/s-w44wOMzqs

BUG=585096

Review-Url: https://codereview.chromium.org/2547563002
Cr-Commit-Position: refs/heads/master@{#436324}

content/child/runtime_features.cc

@@ -42,6 +42,8 @@ static void SetRuntimeFeatureDefaultsForPlatform() {
   // Android does not yet support switching of audio output devices
   WebRuntimeFeatures::enableAudioOutputDevices(false);
   WebRuntimeFeatures::enableAutoplayMutedVideos(true);
+  // Android does not yet support SystemMonitor.
+  WebRuntimeFeatures::enableOnDeviceChange(false);
 #else
   WebRuntimeFeatures::enableNavigatorContentUtils(true);
 #endif  // defined(OS_ANDROID)

third_party/WebKit/LayoutTests/platform/win/virtual/stable/webexposed/global-interface-listing-expected.txt

@@ -3171,10 +3171,12 @@ interface MediaDeviceInfo
     method toJSON
 interface MediaDevices : EventTarget
     attribute @@toStringTag
+    getter ondevicechange
     method constructor
     method enumerateDevices
     method getSupportedConstraints
     method getUserMedia
+    setter ondevicechange
 interface MediaElementAudioSourceNode : AudioSourceNode
     attribute @@toStringTag
     getter mediaElement

third_party/WebKit/LayoutTests/virtual/stable/webexposed/global-interface-listing-expected.txt

@@ -3228,10 +3228,12 @@ interface MediaDeviceInfo
     method toJSON
 interface MediaDevices : EventTarget
     attribute @@toStringTag
+    getter ondevicechange
     method constructor
     method enumerateDevices
     method getSupportedConstraints
     method getUserMedia
+    setter ondevicechange
 interface MediaElementAudioSourceNode : AudioSourceNode
     attribute @@toStringTag
     getter mediaElement

third_party/WebKit/Source/platform/RuntimeEnabledFeatures.in

@@ -155,7 +155,7 @@ NotificationBadge status=stable
 NotificationContentImage status=stable
 NotificationInlineReplies status=experimental
 Notifications status=stable
-OnDeviceChange status=experimental
+OnDeviceChange status=stable
 OrientationEvent
 OriginTrials status=stable
 // Define a sample API for testing integration with the Origin Trials Framework.

third_party/WebKit/Source/web/WebRuntimeFeatures.cpp

@@ -178,6 +178,10 @@ void WebRuntimeFeatures::enableNetworkInformation(bool enable) {
   RuntimeEnabledFeatures::setNetworkInformationEnabled(enable);
 }
 
+void WebRuntimeFeatures::enableOnDeviceChange(bool enable) {
+  RuntimeEnabledFeatures::setOnDeviceChangeEnabled(enable);
+}
+
 void WebRuntimeFeatures::enableOrientationEvent(bool enable) {
   RuntimeEnabledFeatures::setOrientationEventEnabled(enable);
 }

third_party/WebKit/public/web/WebRuntimeFeatures.h

@@ -92,6 +92,7 @@ class WebRuntimeFeatures {
   BLINK_EXPORT static void enableNotificationConstructor(bool);
   BLINK_EXPORT static void enableNotificationContentImage(bool);
   BLINK_EXPORT static void enableNotifications(bool);
+  BLINK_EXPORT static void enableOnDeviceChange(bool);
   BLINK_EXPORT static void enableOrientationEvent(bool);
   BLINK_EXPORT static void enableOverlayScrollbars(bool);
   BLINK_EXPORT static void enablePagePopup(bool);