media: Create Mojo StructTraits for VideoFrame

media/mojo/common/mojo_shared_buffer_video_frame.h

Index: media/mojo/common/mojo_shared_buffer_video_frame.h
diff --git a/media/mojo/common/mojo_shared_buffer_video_frame.h b/media/mojo/common/mojo_shared_buffer_video_frame.h
index 945f43e51f38ec57e6279a8e8e9538d6e7772fd7..7cd054779f58f54786927f327e8924b50a33a9c1 100644
--- a/media/mojo/common/mojo_shared_buffer_video_frame.h
+++ b/media/mojo/common/mojo_shared_buffer_video_frame.h
@@ -72,6 +72,14 @@ class MojoSharedBufferVideoFrame : public VideoFrame {
   // |plane| specified.
   size_t PlaneOffset(size_t plane) const;
 
+  // Returns the mojo shared memory handle. This object continues to own the
+  // handle. Caller should duplicate the handle if they want to keep a copy of
+  // the shared memory.

[dcheng, 2017/06/08 09:41:08]

Nit: the fact that this returns a const reference is a hint that no ownership
transfer happened. I would reword the last part to say something about "Callers
must duplicate the handle if they to extend the lifetime of the shared memory",
since we're not really copying it

[sandersd (OOO until July 31), 2017/06/08 20:10:09]

Done.

+  const mojo::SharedBufferHandle& Handle() const;
+
+  // Returns the size of the shared memory.
+  size_t MappedSize() const;
+
   // Sets the callback to be called to free the shared buffer. If not null,
   // it is called on destruction, and is passed ownership of |handle|.
   void SetMojoSharedBufferDoneCB(
@@ -102,14 +110,6 @@ class MojoSharedBufferVideoFrame : public VideoFrame {
             size_t u_offset,
             size_t v_offset);
 
-  // Returns the mojo shared memory handle. This object continues to own the
-  // handle. Caller should call duplicate the handle if they want to keep a
-  // copy of the shared memory.
-  const mojo::SharedBufferHandle& Handle() const;
-
-  // Returns the size of the shared memory.
-  size_t MappedSize() const;
-
   uint8_t* shared_buffer_data() {
     return reinterpret_cast<uint8_t*>(shared_buffer_mapping_.get());
   };