Add srcObject attribute of type MediaStream to HTMLMediaElement.

third_party/WebKit/Source/modules/modules.gypi

 {
   'includes': [
     '../core/core_generated.gypi',
     'modules_generated.gypi',
   ],
   'variables': {
     # Experimental hooks for embedder to provide extra IDL and source files.
     #
     # Note: this is not a supported API. If you rely on this, you will be broken
     # from time to time as the code generator changes in backward incompatible
@@ skipping 351 matching lines @@
       'geofencing/WorkerNavigatorGeofencing.idl',
       'geolocation/NavigatorGeolocation.idl',
       'indexeddb/WindowIndexedDatabase.idl',
       'indexeddb/WorkerGlobalScopeIndexedDatabase.idl',
       'installedapp/NavigatorInstalledApp.idl',
       'mediacapturefromelement/HTMLCanvasElementCapture.idl',
       'mediacapturefromelement/HTMLMediaElementCapture.idl',
       'mediasession/HTMLMediaElementMediaSession.idl',
       'mediasource/HTMLVideoElementMediaSource.idl',
       'mediasource/URLMediaSource.idl',
+      'mediastream/HTMLMediaElementMediaStream.idl',
       'mediastream/NavigatorMediaStream.idl',
       'mediastream/NavigatorUserMedia.idl',
       'mediastream/URLMediaStream.idl',
       'mediastream/WindowMediaStream.idl',
       'navigatorconnect/NavigatorServices.idl',
       'navigatorconnect/ServiceWorkerGlobalScopeNavigatorConnect.idl',
       'navigatorconnect/WorkerNavigatorServices.idl',
       'navigatorcontentutils/NavigatorContentUtils.idl',
       'nfc/NavigatorNFC.idl',
       'netinfo/NavigatorNetworkInformation.idl',
@@ skipping 830 matching lines @@
       'mediasource/SourceBufferList.cpp',
       'mediasource/SourceBufferList.h',
       'mediasource/TrackDefault.cpp',
       'mediasource/TrackDefault.h',
       'mediasource/TrackDefaultList.cpp',
       'mediasource/TrackDefaultList.h',
       'mediasource/URLMediaSource.cpp',
       'mediasource/URLMediaSource.h',
       'mediasource/VideoPlaybackQuality.cpp',
       'mediasource/VideoPlaybackQuality.h',
+      'mediastream/HTMLMediaElementMediaStream.cpp',
+      'mediastream/HTMLMediaElementMediaStream.h',
       'mediastream/MediaConstraintsImpl.cpp',
       'mediastream/MediaConstraintsImpl.h',
       'mediastream/MediaDeviceInfo.cpp',
       'mediastream/MediaDeviceInfo.h',
       'mediastream/MediaDevices.cpp',
       'mediastream/MediaDevices.h',
       'mediastream/MediaDevicesRequest.cpp',
       'mediastream/MediaDevicesRequest.h',
       'mediastream/MediaErrorState.cpp',
       'mediastream/MediaErrorState.h',
@@ skipping 753 matching lines @@
       'webaudio/AudioBasicProcessorHandlerTest.cpp',
       'webaudio/ConvolverNodeTest.cpp',
       'webaudio/DynamicsCompressorNodeTest.cpp',
       'webaudio/ScriptProcessorNodeTest.cpp',
       'webaudio/StereoPannerNodeTest.cpp',
       'websockets/DOMWebSocketTest.cpp',
       'websockets/DocumentWebSocketChannelTest.cpp',
     ],
   },
 }