Reland of New method I420Buffer::SetToBlack.

webrtc/common_video/include/video_frame_buffer.h

Index: webrtc/common_video/include/video_frame_buffer.h
diff --git a/webrtc/common_video/include/video_frame_buffer.h b/webrtc/common_video/include/video_frame_buffer.h
index 984bd50d674e78d7e7aedfc252fcfef8810b6963..890922f21be2dfa9896db25b5627ebc8be0b0c53 100644
--- a/webrtc/common_video/include/video_frame_buffer.h
+++ b/webrtc/common_video/include/video_frame_buffer.h
@@ -87,8 +87,18 @@ class I420Buffer : public VideoFrameBuffer {
  public:
   I420Buffer(int width, int height);
   I420Buffer(int width, int height, int stride_y, int stride_u, int stride_v);
+
+  // Sets all three planes to all zeros. Used to work around for
+  // quirks in memory checkers
+  // (https://bugs.chromium.org/p/libyuv/issues/detail?id=377) and
+  // ffmpeg (http://crbug.com/390941).
+  // TODO(nisse): Should be deleted if/when those issues are resolved
+  // in a better way.
   void InitializeData();
 
+  // Sets the frame buffer to all black.
+  void SetToBlack();
+
   int width() const override;
   int height() const override;
   const uint8_t* DataY() const override;