ObjC: Marshal all VideoTrackSource methods to the signaling thread

This CL makes sure the real VideoTrackSourceInterface implementation is
destroyed on the signaling thread and marshals all method calls to the
signaling thread. This is done using VideoTrackSourceProxy.

Bug: webrtc:7767
Change-Id: Iba3b67bb32a684ba289bc8b9981585ea58084359
Reviewed-on: https://chromium-review.googlesource.com/526634
Commit-Queue: Magnus Jedvert <magjed@webrtc.org>
Reviewed-by: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#18476}

webrtc/sdk/objc/Framework/Classes/PeerConnection/RTCPeerConnectionFactory.mm

@@ -23,6 +23,7 @@
 
 #include "Video/objcvideotracksource.h"
 #include "VideoToolbox/videocodecfactory.h"
+#include "webrtc/api/videosourceproxy.h"
 
 @implementation RTCPeerConnectionFactory {
   std::unique_ptr<rtc::Thread> _networkThread;
@@ -91,7 +92,10 @@
 - (RTCVideoSource *)videoSource {
   rtc::scoped_refptr<webrtc::ObjcVideoTrackSource> objcVideoTrackSource(
       new rtc::RefCountedObject<webrtc::ObjcVideoTrackSource>());
-  return [[RTCVideoSource alloc] initWithNativeVideoSource:objcVideoTrackSource];
+  return [[RTCVideoSource alloc]
+      initWithNativeVideoSource:webrtc::VideoTrackSourceProxy::Create(_signalingThread.get(),
+                                                                      _workerThread.get(),
+                                                                      objcVideoTrackSource)];
 }
 
 - (RTCVideoTrack *)videoTrackWithSource:(RTCVideoSource *)source

webrtc/sdk/objc/Framework/Classes/PeerConnection/RTCVideoSource.mm

@@ -10,9 +10,17 @@
 
 #import "RTCVideoSource+Private.h"
 
+#include "webrtc/api/videosourceproxy.h"
 #include "webrtc/base/checks.h"
 #include "webrtc/sdk/objc/Framework/Classes/Video/objcvideotracksource.h"
 
+static webrtc::ObjcVideoTrackSource *getObjcVideoSource(
+    const rtc::scoped_refptr<webrtc::VideoTrackSourceInterface> nativeSource) {
+  webrtc::VideoTrackSourceProxy *proxy_source =
+      static_cast<webrtc::VideoTrackSourceProxy *>(nativeSource.get());
+  return static_cast<webrtc::ObjcVideoTrackSource *>(proxy_source->internal());
+}
+
 // TODO(magjed): Refactor this class and target ObjcVideoTrackSource only once
 // RTCAVFoundationVideoSource is gone. See http://crbug/webrtc/7177 for more
 // info.
@@ -43,12 +51,11 @@
 }
 
 - (void)capturer:(RTCVideoCapturer *)capturer didCaptureVideoFrame:(RTCVideoFrame *)frame {
-  static_cast<webrtc::ObjcVideoTrackSource *>(_nativeVideoSource.get())->OnCapturedFrame(frame);
+  getObjcVideoSource(_nativeVideoSource)->OnCapturedFrame(frame);
 }
 
 - (void)adaptOutputFormatToWidth:(int)width height:(int)height fps:(int)fps {
-  static_cast<webrtc::ObjcVideoTrackSource *>(_nativeVideoSource.get())
-      ->OnOutputFormatRequest(width, height, fps);
+  getObjcVideoSource(_nativeVideoSource)->OnOutputFormatRequest(width, height, fps);
 }
 
 #pragma mark - Private