H264: Improve FFmpeg decoder performance by using I420BufferPool.

webrtc/common_video/video_frame_buffer.cc

Index: webrtc/common_video/video_frame_buffer.cc
diff --git a/webrtc/common_video/video_frame_buffer.cc b/webrtc/common_video/video_frame_buffer.cc
index 492bc495876a6a21b080252686991c89a2f5840b..e3c114c99b7175e6184b33fb480fd0f61d481497 100644
--- a/webrtc/common_video/video_frame_buffer.cc
+++ b/webrtc/common_video/video_frame_buffer.cc
@@ -18,6 +18,14 @@ static const int kBufferAlignment = 64;
 
 namespace webrtc {
 
+namespace {
+
+int I420DataSize(int height, int stride_y, int stride_u, int stride_v) {
+  return stride_y * height + (stride_u + stride_v) * ((height + 1) / 2);
+}
+
+}  // namespace
+
 uint8_t* VideoFrameBuffer::MutableData(PlaneType type) {
   RTC_NOTREACHED();
   return nullptr;
@@ -40,7 +48,7 @@ I420Buffer::I420Buffer(int width,
       stride_u_(stride_u),
       stride_v_(stride_v),
       data_(static_cast<uint8_t*>(AlignedMalloc(
-          stride_y * height + (stride_u + stride_v) * ((height + 1) / 2),
+          I420DataSize(height, stride_y, stride_u, stride_v),
           kBufferAlignment))) {
   RTC_DCHECK_GT(width, 0);
   RTC_DCHECK_GT(height, 0);
@@ -81,6 +89,10 @@ uint8_t* I420Buffer::MutableData(PlaneType type) {
       static_cast<const VideoFrameBuffer*>(this)->data(type));
 }
 
+int I420Buffer::DataSize() const {
+  return I420DataSize(height_, stride_y_, stride_u_, stride_v_);
+}
+
 int I420Buffer::stride(PlaneType type) const {
   switch (type) {
     case kYPlane: