cc: Add GpuMemoryBufferHandle to TextureMailbox

cc/resources/texture_mailbox.h

Index: cc/resources/texture_mailbox.h
diff --git a/cc/resources/texture_mailbox.h b/cc/resources/texture_mailbox.h
index 8dcf98ed3802e0ade6468d5f95f3f99631a69fe5..681864ed01d79c2c510f62c355ee1f7a71135dba 100644
--- a/cc/resources/texture_mailbox.h
+++ b/cc/resources/texture_mailbox.h
@@ -14,6 +14,7 @@
 #include "cc/base/cc_export.h"
 #include "gpu/command_buffer/common/mailbox_holder.h"
 #include "ui/gfx/geometry/size.h"
+#include "ui/gfx/gpu_memory_buffer.h"
 
 namespace cc {
 class SharedBitmap;
@@ -31,9 +32,11 @@ class CC_EXPORT TextureMailbox {
                  const gpu::SyncToken& sync_token,
                  uint32_t target,
                  const gfx::Size& size_in_pixels,
+                 const gfx::GpuMemoryBufferHandle& gpu_memory_buffer_handle,
                  bool is_overlay_candidate,
                  bool secure_output_only);
   TextureMailbox(SharedBitmap* shared_bitmap, const gfx::Size& size_in_pixels);
+  TextureMailbox(const TextureMailbox& other);
 
   ~TextureMailbox();
 
@@ -73,6 +76,7 @@ class CC_EXPORT TextureMailbox {
   gpu::MailboxHolder mailbox_holder_;
   SharedBitmap* shared_bitmap_;
   gfx::Size size_in_pixels_;
+  gfx::GpuMemoryBufferHandle gpu_memory_buffer_handle_;

[reveman, 2016/04/29 10:05:05]

Can this be a "gfx::GpuMemoryBuffer*" and the handle is only created when this
needs to be sent over IPC? In the case of the UI compositor there might not be a
need for creating a handle.

[ccameron, 2016/04/29 17:33:32]

To me it felt much more natural to use a gfx::GpuMemoryBufferHandle here as
compared with a pointer. 

Couple of reasons:
- The cc::ResourceProvider takes ownership (via unique_ptr) of the
GpuMemoryBuffer, which would create lifetime issues for the object (both cc/ and
the caller want to own the GMB object)

- I prototyped plugging this in to the video code, and the GMB handle fit very
cleanly with
https://code.google.com/p/chromium/codesearch#chromium/src/media/base/video_f...

So to me it seems that passing via handle is better (but I do have a Mac-centric
worldview).

   bool is_overlay_candidate_;
   bool secure_output_only_;
   bool nearest_neighbor_;