Zero initialize the first allocation of a VideoFrame.

Replicates FFmpeg's behavior for frame allocation.  They do not zero
the frame on subsequent pool reuse, so I have not done so either.

BUG=390941,390944,390945
TEST=new unittest.

Review URL: https://codereview.chromium.org/383893002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@282775 0039d316-1c4b-4281-b951-d872f2087c98

media/base/video_frame.cc

@@ -618,10 +618,13 @@ void VideoFrame::AllocateYUV() {
   // overreads by one line in some cases, see libavcodec/utils.c:
   // avcodec_align_dimensions2() and libavcodec/x86/h264_chromamc.asm:
   // put_h264_chroma_mc4_ssse3().
+  const size_t data_size =
+      y_bytes + (uv_bytes * 2 + uv_stride) + a_bytes + kFrameSizePadding;
   uint8* data = reinterpret_cast<uint8*>(
-      base::AlignedAlloc(
-          y_bytes + (uv_bytes * 2 + uv_stride) + a_bytes + kFrameSizePadding,
-          kFrameAddressAlignment));
+      base::AlignedAlloc(data_size, kFrameAddressAlignment));
+  // FFmpeg expects the initialize allocation to be zero-initialized.  Failure
+  // to do so can lead to unitialized value usage.  See http://crbug.com/390941
+  memset(data, 0, data_size);
   no_longer_needed_cb_ = base::Bind(&ReleaseData, data);
   COMPILE_ASSERT(0 == VideoFrame::kYPlane, y_plane_data_must_be_index_0);
   data_[VideoFrame::kYPlane] = data;

media/base/video_frame_unittest.cc

@@ -308,4 +308,17 @@ TEST(VideoFrame, TextureNoLongerNeededCallbackAfterTakingAndReleasingMailbox) {
   EXPECT_EQ(release_sync_points, called_sync_points);
 }
 
+TEST(VideoFrame, ZeroInitialized) {
+  const int kWidth = 64;
+  const int kHeight = 48;
+  const base::TimeDelta kTimestamp = base::TimeDelta::FromMicroseconds(1337);
+
+  gfx::Size size(kWidth, kHeight);
+  scoped_refptr<media::VideoFrame> frame = VideoFrame::CreateFrame(
+      media::VideoFrame::YV12, size, gfx::Rect(size), size, kTimestamp);
+
+  for (size_t i = 0; i < VideoFrame::NumPlanes(frame->format()); ++i)
+    EXPECT_EQ(0, frame->data(i)[0]);
+}
+
 }  // namespace media