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 376 matching lines @@
       'push_messaging/ServiceWorkerGlobalScopePush.idl',
       'push_messaging/ServiceWorkerRegistrationPush.idl',
       'quota/NavigatorStorageQuota.idl',
       'quota/WindowQuota.idl',
       'quota/WorkerNavigatorStorageQuota.idl',
       'remoteplayback/HTMLMediaElementRemotePlayback.idl',
       'screen_orientation/ScreenScreenOrientation.idl',
       'serviceworkers/NavigatorServiceWorker.idl',
       'speech/WindowSpeech.idl',
       'speech/WindowSpeechSynthesis.idl',
+      'srcobject/HTMLMediaElementSrcObject.idl',
       'storage/WindowStorage.idl',
       'vibration/NavigatorVibration.idl',
       'vr/NavigatorVRDevice.idl',
       'wake_lock/ScreenWakeLock.idl',
       'webaudio/WindowWebAudio.idl',
       'webdatabase/WindowWebDatabase.idl',
       'webgl/WebGL2RenderingContextBase.idl',
       'webgl/WebGLRenderingContextBase.idl',
       'webmidi/NavigatorWebMIDI.idl',
       'webusb/NavigatorUSB.idl',
@@ skipping 1098 matching lines @@
       'speech/SpeechRecognitionResultList.cpp',
       'speech/SpeechRecognitionResultList.h',
       'speech/SpeechSynthesis.cpp',
       'speech/SpeechSynthesis.h',
       'speech/SpeechSynthesisEvent.cpp',
       'speech/SpeechSynthesisEvent.h',
       'speech/SpeechSynthesisUtterance.cpp',
       'speech/SpeechSynthesisUtterance.h',
       'speech/SpeechSynthesisVoice.cpp',
       'speech/SpeechSynthesisVoice.h',
+      'srcobject/HTMLMediaElementSrcObject.cpp',
+      'srcobject/HTMLMediaElementSrcObject.h',
       'storage/DOMWindowStorage.cpp',
       'storage/DOMWindowStorage.h',
       'storage/DOMWindowStorageController.cpp',
       'storage/DOMWindowStorageController.h',
       'storage/InspectorDOMStorageAgent.cpp',
       'storage/InspectorDOMStorageAgent.h',
       'storage/Storage.cpp',
       'storage/Storage.h',
       'storage/StorageArea.cpp',
       'storage/StorageArea.h',
@@ skipping 456 matching lines @@
       'webaudio/AudioBasicProcessorHandlerTest.cpp',
       'webaudio/ConvolverNodeTest.cpp',
       'webaudio/DynamicsCompressorNodeTest.cpp',
       'webaudio/ScriptProcessorNodeTest.cpp',
       'webaudio/StereoPannerNodeTest.cpp',
       'websockets/DOMWebSocketTest.cpp',
       'websockets/DocumentWebSocketChannelTest.cpp',
     ],
   },
 }