Added Web Share (navigator.share) experimental web API (stub).

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 392 matching lines @@
       'srcobject/HTMLMediaElementSrcObject.idl',
       'storage/WindowStorage.idl',
       'vibration/NavigatorVibration.idl',
       'vr/NavigatorVR.idl',
       'wake_lock/ScreenWakeLock.idl',
       'webaudio/WindowWebAudio.idl',
       'webdatabase/WindowWebDatabase.idl',
       'webgl/WebGL2RenderingContextBase.idl',
       'webgl/WebGLRenderingContextBase.idl',
       'webmidi/NavigatorWebMIDI.idl',
+      'webshare/NavigatorShare.idl',
       'webusb/NavigatorUSB.idl',
     ],
     # interfaces that inherit from Event
     'modules_event_idl_files': [
       'app_banner/BeforeInstallPromptEvent.idl',
       'background_sync/SyncEvent.idl',
       'device_light/DeviceLightEvent.idl',
       'device_orientation/DeviceMotionEvent.idl',
       'device_orientation/DeviceOrientationEvent.idl',
       'encryptedmedia/MediaEncryptedEvent.idl',
@@ skipping 1506 matching lines @@
       'webmidi/MIDIMessageEvent.h',
       'webmidi/MIDIPortMap.h',
       'webmidi/MIDIOutput.cpp',
       'webmidi/MIDIOutput.h',
       'webmidi/MIDIOutputMap.cpp',
       'webmidi/MIDIOutputMap.h',
       'webmidi/MIDIPort.cpp',
       'webmidi/MIDIPort.h',
       'webmidi/NavigatorWebMIDI.cpp',
       'webmidi/NavigatorWebMIDI.h',
+      'webshare/NavigatorShare.cpp',
+      'webshare/NavigatorShare.h',
       'websockets/CloseEvent.cpp',
       'websockets/CloseEvent.h',
       'websockets/DOMWebSocket.cpp',
       'websockets/DOMWebSocket.h',
       'websockets/DocumentWebSocketChannel.cpp',
       'websockets/DocumentWebSocketChannel.h',
       'websockets/InspectorWebSocketEvents.cpp',
       'websockets/InspectorWebSocketEvents.h',
       'websockets/WebSocketChannel.cpp',
       'websockets/WebSocketChannel.h',
@@ skipping 110 matching lines @@
       'webaudio/ConvolverNodeTest.cpp',
       'webaudio/DynamicsCompressorNodeTest.cpp',
       'webaudio/ScriptProcessorNodeTest.cpp',
       'webaudio/StereoPannerNodeTest.cpp',
       'webdatabase/QuotaTrackerTest.cpp',
       'websockets/DOMWebSocketTest.cpp',
       'websockets/DocumentWebSocketChannelTest.cpp',
     ],
   },
 }