WebRTC: One WebRTC Video can have both SW and HW VideoFrame.

SkCanvasVideoRenderer assumes that the VideoFrames belonging to one WebRTC
video are always either software VideoFrame or hardware VideoFrame.
However, it's not true. VideoFrame can be changed each frame.

TEST=content_browsertests WebRtcBrowserTest.CallAndVerify* on Nexus5
BUG=448014

Review URL: https://codereview.chromium.org/848683003

Cr-Commit-Position: refs/heads/master@{#311468}

media/filters/skcanvas_video_renderer.cc

@@ -429,10 +429,14 @@ void SkCanvasVideoRenderer::Paint(const scoped_refptr<VideoFrame>& video_frame,
     if (accelerated_last_frame_.isNull() ||
         video_frame->timestamp() != accelerated_last_frame_timestamp_) {
       if (video_frame->format() == VideoFrame::NATIVE_TEXTURE) {
+        // Draw HW Video on HW Canvas.
         DCHECK(context_3d.gl);
         DCHECK(context_3d.gr_context);
-        // Draw HW Video on HW Canvas.
-        DCHECK(!accelerated_generator_);
+        if (accelerated_generator_) {
+          // Reset SkBitmap used in SWVideo-to-HWCanvas path.
+          accelerated_last_frame_.reset();
+          accelerated_generator_ = nullptr;
+        }
         if (!CopyVideoFrameTextureToSkBitmapTexture(
                 video_frame.get(), &accelerated_last_frame_, context_3d)) {
           NOTREACHED();
@@ -440,6 +444,10 @@ void SkCanvasVideoRenderer::Paint(const scoped_refptr<VideoFrame>& video_frame,
         }
       } else {
         // Draw SW Video on HW Canvas.
+        if (!accelerated_generator_ && !accelerated_last_frame_.isNull()) {
+          // Reset SkBitmap used in HWVideo-to-HWCanvas path.
+          accelerated_last_frame_.reset();
+        }
         accelerated_generator_ = new VideoImageGenerator(video_frame);
 
         // Note: This takes ownership of |accelerated_generator_|.