Replace SetCapturer and SetCaptureDevice by SetSource.

webrtc/pc/channel.h

Index: webrtc/pc/channel.h
diff --git a/webrtc/pc/channel.h b/webrtc/pc/channel.h
index f72818924d598b062280e858711e05ea8c702add..59e166f87b33a713d6599e2f118d9ad38933717f 100644
--- a/webrtc/pc/channel.h
+++ b/webrtc/pc/channel.h
@@ -26,8 +26,8 @@
 #include "webrtc/media/base/mediachannel.h"
 #include "webrtc/media/base/mediaengine.h"
 #include "webrtc/media/base/streamparams.h"
-#include "webrtc/media/base/videocapturer.h"
 #include "webrtc/media/base/videosinkinterface.h"
+#include "webrtc/media/base/videosourceinterface.h"
 #include "webrtc/p2p/base/transportcontroller.h"
 #include "webrtc/p2p/client/socketmonitor.h"
 #include "webrtc/pc/audiomonitor.h"
@@ -444,7 +444,10 @@ class VideoChannel : public BaseChannel {
   // ssrc here as the "key".
   // Passes ownership of the capturer to the channel.
   bool AddScreencast(uint32_t ssrc, VideoCapturer* capturer);
-  bool SetCapturer(uint32_t ssrc, VideoCapturer* capturer);
+  // Register a source. The |ssrc| must correspond to a registered
+  // send stream.

[pthatcher1, 2016/03/05 01:45:41]

We should specify what happens if it isn't (ie nothing, except a debug build
will explode)

[nisse-webrtc, 2016/03/15 16:28:00]

The current implementation will always explode, except if source is NULL. I
don't quite like the exception, but it seemed hard to avoid (I think I described
the problem a week or two ago).

And do we really need to document in which way things break in case a caller
violates the documented interface?

+  void SetSource(uint32_t ssrc,
+                 rtc::VideoSourceInterface<cricket::VideoFrame>* source);
   bool RemoveScreencast(uint32_t ssrc);
   // True if we've added a screencast.  Doesn't matter if the capturer
   // has been started or not.