Implement timestamp translation/filter in VideoCapturer.

webrtc/media/base/fakevideocapturer.h

Index: webrtc/media/base/fakevideocapturer.h
diff --git a/webrtc/media/base/fakevideocapturer.h b/webrtc/media/base/fakevideocapturer.h
index 026bf80a7b15f0f83f94bf66a9fe52eb23bc7cd5..dc4236e7eca02c29f5b4c9a89bc5407b43f42f2a 100644
--- a/webrtc/media/base/fakevideocapturer.h
+++ b/webrtc/media/base/fakevideocapturer.h
@@ -151,6 +151,10 @@ class FakeVideoCapturer : public cricket::VideoCapturer {
 
   webrtc::VideoRotation GetRotation() { return rotation_; }
 
+  // Expose as public, for testing.
+  using VideoCapturer::AdaptFrame;
+  using VideoCapturer::clip_bias_us;
+
  private:
   bool running_;
   int64_t initial_timestamp_;