Replace SetCapturer and SetCaptureDevice by SetSource.
Drop return value.

BUG=webrtc:5426

Review URL: https://codereview.webrtc.org/1766653002

Cr-Commit-Position: refs/heads/master@{#12291}
diff --git a/webrtc/api/webrtcsession.cc b/webrtc/api/webrtcsession.cc
index f546285..f51d4cd 100644
--- a/webrtc/api/webrtcsession.cc
+++ b/webrtc/api/webrtcsession.cc
@@ -1261,8 +1261,9 @@
   return voice_channel_->SetRtpParameters(ssrc, parameters);
 }
 
-bool WebRtcSession::SetCaptureDevice(uint32_t ssrc,
-                                     cricket::VideoCapturer* camera) {
+bool WebRtcSession::SetSource(
+    uint32_t ssrc,
+    rtc::VideoSourceInterface<cricket::VideoFrame>* source) {
   ASSERT(signaling_thread()->IsCurrent());
 
   if (!video_channel_) {
@@ -1271,13 +1272,7 @@
     LOG(LS_WARNING) << "Video not used in this call.";
     return false;
   }
-  if (!video_channel_->SetCapturer(ssrc, camera)) {
-    // Allow that SetCapturer fail if |camera| is NULL but assert otherwise.
-    // This in the normal case when the underlying media channel has already
-    // been deleted.
-    ASSERT(camera == NULL);
-    return false;
-  }
+  video_channel_->SetSource(ssrc, source);
   return true;
 }