media: Remove SkCanvasVideoRenderer cache invalidation.

When VideoFrame carries one native texture, with a GL_TEXTURE_2D target,
we assumed we could avoid caching the created SkImage, since we just used
the texture directly for drawing.
Unfortunately if we're drawing to a software canvas we need to read the pixels
back from the texture, and that is expensive.
Keeping the same SkImage allows Skia to cache the expensive operation.

BUG=521531

Review URL: https://codereview.chromium.org/1320613003

Cr-Commit-Position: refs/heads/master@{#345799}

media/blink/skcanvas_video_renderer.cc

@@ -127,12 +127,6 @@ skia::RefPtr<SkImage> NewSkImageFromVideoFrameYUVTextures(
   return skia::AdoptRef(img);
 }
 
-bool ShouldCacheVideoFrameSkImage(const VideoFrame* video_frame) {
-  return !video_frame->HasTextures() ||
-         media::VideoFrame::NumPlanes(video_frame->format()) != 1 ||
-         video_frame->mailbox_holder(0).texture_target != GL_TEXTURE_2D;
-}
-
 // Creates a SkImage from a |video_frame| backed by native resources.
 // The SkImage will take ownership of the underlying resource.
 skia::RefPtr<SkImage> NewSkImageFromVideoFrameNative(
@@ -388,9 +382,6 @@ void SkCanvasVideoRenderer::Paint(const scoped_refptr<VideoFrame>& video_frame,
   // Make sure to flush so we can remove the videoframe from the generator.
   canvas->flush();
 
-  if (!ShouldCacheVideoFrameSkImage(video_frame.get()))
-    ResetCache();
-
   if (video_frame->HasTextures()) {
     DCHECK(gl);
     SyncPointClientImpl client(gl);