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.h b/webrtc/api/webrtcsession.h
index 01ec526..752b20f 100644
--- a/webrtc/api/webrtcsession.h
+++ b/webrtc/api/webrtcsession.h
@@ -34,7 +34,6 @@
 class ChannelManager;
 class DataChannel;
 class StatsReport;
-class VideoCapturer;
 class VideoChannel;
 class VoiceChannel;
 
@@ -250,7 +249,9 @@
                              const RtpParameters& parameters) override;
 
   // Implements VideoMediaProviderInterface.
-  bool SetCaptureDevice(uint32_t ssrc, cricket::VideoCapturer* camera) override;
+  bool SetSource(
+      uint32_t ssrc,
+      rtc::VideoSourceInterface<cricket::VideoFrame>* source) override;
   void SetVideoPlayout(
       uint32_t ssrc,
       bool enable,