Revert to zero-initializing buffers for FFmpegVideoDecoder

media/base/video_frame_pool.cc

Index: media/base/video_frame_pool.cc
diff --git a/media/base/video_frame_pool.cc b/media/base/video_frame_pool.cc
index 4951941d06be5d7ffe9e08e0959fb303ba7661c5..8c8870c7a80f928a0db28c07ef4fbb27014e21b0 100644
--- a/media/base/video_frame_pool.cc
+++ b/media/base/video_frame_pool.cc
@@ -17,14 +17,13 @@ class VideoFramePool::PoolImpl
  public:
   PoolImpl();
 
-  // Returns a frame from the pool that matches the specified
-  // parameters or creates a new frame if no suitable frame exists in
-  // the pool. The pool is drained if no matching frame is found.
+  // See VideoFramePool::CreateFrame() for usage.
   scoped_refptr<VideoFrame> CreateFrame(VideoPixelFormat format,
                                         const gfx::Size& coded_size,
                                         const gfx::Rect& visible_rect,
                                         const gfx::Size& natural_size,
-                                        base::TimeDelta timestamp);
+                                        base::TimeDelta timestamp,
+                                        bool zero_new_frames);
 
   // Shuts down the frame pool and releases all frames in |frames_|.
   // Once this is called frames will no longer be inserted back into
@@ -60,7 +59,8 @@ scoped_refptr<VideoFrame> VideoFramePool::PoolImpl::CreateFrame(
     const gfx::Size& coded_size,
     const gfx::Rect& visible_rect,
     const gfx::Size& natural_size,
-    base::TimeDelta timestamp) {
+    base::TimeDelta timestamp,
+    bool zero_new_frames) {
   base::AutoLock auto_lock(lock_);
   DCHECK(!is_shutdown_);
 
@@ -83,6 +83,8 @@ scoped_refptr<VideoFrame> VideoFramePool::PoolImpl::CreateFrame(
   if (!frame.get()) {
     frame = VideoFrame::CreateFrame(
         format, coded_size, visible_rect, natural_size, timestamp);
+    if (zero_new_frames)
+      memset(frame->data(0), 0, frame->allocated_size());

[miu, 2015/08/04 20:16:22]

You have enough information to memset() all the memory without having this extra
allocated_size() property.  Meaning:

  if (zero_new_frames) {
    const size_t num_planes = VideoFrame::NumPlanes(frame->format());
    for (size_t i = 0; i < num_planes; ++i) {
      memset(frame->data(i),
             0,
             VideoFrame::PlaneSize(frame->format(),
                                   i,
                                   frame->coded_size()).GetArea()));
    }
  }

[DaleCurtis, 2015/08/04 21:20:52]

This doesn't include the padding around the frame or the extra U plane
allocation.  See l.889

[miu, 2015/08/06 21:23:30]

Okay, but is it enough to ensure FFMPEG isn't reading uninitialized data? 
Basically, I'm opposed to adding |allocated_size| to VideoFrames just for this
one edge case.  Let's be sure we absolutely have to do this.

BTW--If we "absolutely have to do this," we should just have
VideoFrame::CreateFrame() do it (e.g., in AllocateYUV() or nearby), rather than
expose this as an externally-handled thing.

   }
 
   scoped_refptr<VideoFrame> wrapped_frame = VideoFrame::WrapVideoFrame(
@@ -119,9 +121,10 @@ scoped_refptr<VideoFrame> VideoFramePool::CreateFrame(
     const gfx::Size& coded_size,
     const gfx::Rect& visible_rect,
     const gfx::Size& natural_size,
-    base::TimeDelta timestamp) {
+    base::TimeDelta timestamp,
+    bool zero_new_frames) {
   return pool_->CreateFrame(format, coded_size, visible_rect, natural_size,
-                            timestamp);
+                            timestamp, zero_new_frames);
 }
 
 size_t VideoFramePool::GetPoolSizeForTesting() const {