media/vpx: Add support for VP9 alpha channel

media/base/video_frame.cc

Index: media/base/video_frame.cc
diff --git a/media/base/video_frame.cc b/media/base/video_frame.cc
index bc5e8e779a7052afab5503dbe7e02d00a87a6682..2de6bd36d5cdffb60956aa515a3824671db29b7d 100644
--- a/media/base/video_frame.cc
+++ b/media/base/video_frame.cc
@@ -287,6 +287,48 @@ scoped_refptr<VideoFrame> VideoFrame::WrapExternalYuvGpuMemoryBuffers(
   return frame;
 }
 
+// static
+scoped_refptr<VideoFrame> VideoFrame::WrapExternalYuvaData(
+    VideoPixelFormat format,
+    const gfx::Size& coded_size,
+    const gfx::Rect& visible_rect,
+    const gfx::Size& natural_size,
+    int32_t y_stride,
+    int32_t u_stride,
+    int32_t v_stride,
+    int32_t a_stride,
+    uint8_t* y_data,
+    uint8_t* u_data,
+    uint8_t* v_data,
+    uint8_t* a_data,
+    base::TimeDelta timestamp) {
+  const StorageType storage = STORAGE_UNOWNED_MEMORY;
+  if (!IsValidConfig(format, storage, coded_size, visible_rect, natural_size)) {
+    LOG(DFATAL) << __FUNCTION__ << " Invalid config."
+                << ConfigToString(format, storage, coded_size, visible_rect,
+                                  natural_size);
+    return nullptr;
+  }
+
+  if (NumPlanes(format) != 4) {
+    LOG(DFATAL) << "Expecting Y, U, V and A planes to be present for the video"
+                << " format.";
+    return nullptr;
+  }
+
+  scoped_refptr<VideoFrame> frame(new VideoFrame(
+      format, storage, coded_size, visible_rect, natural_size, timestamp));
+  frame->strides_[kYPlane] = y_stride;
+  frame->strides_[kUPlane] = u_stride;
+  frame->strides_[kVPlane] = v_stride;
+  frame->strides_[kAPlane] = a_stride;
+  frame->data_[kYPlane] = y_data;
+  frame->data_[kUPlane] = u_data;
+  frame->data_[kVPlane] = v_data;
+  frame->data_[kAPlane] = a_data;
+  return frame;
+}
+
 #if defined(OS_LINUX)
 // static
 scoped_refptr<VideoFrame> VideoFrame::WrapExternalDmabufs(