Replace context parenting by sharing through mailboxes

content/common/gpu/gpu_command_buffer_stub.h

Index: content/common/gpu/gpu_command_buffer_stub.h
diff --git a/content/common/gpu/gpu_command_buffer_stub.h b/content/common/gpu/gpu_command_buffer_stub.h
index f874f46c433c8521677454f604d4426f88b1d5d0..dc1c4acef300a238a008d0e97c4528c613cc980d 100644
--- a/content/common/gpu/gpu_command_buffer_stub.h
+++ b/content/common/gpu/gpu_command_buffer_stub.h
@@ -32,6 +32,7 @@
 #include "ui/surface/transport_dib.h"
 
 namespace gpu {
+struct Mailbox;
 namespace gles2 {
 class ImageManager;
 class MailboxManager;
@@ -149,9 +150,7 @@ class GpuCommandBufferStub
   void OnInitialize(base::SharedMemoryHandle shared_state_shm,
                     IPC::Message* reply_message);
   void OnSetGetBuffer(int32 shm_id, IPC::Message* reply_message);
-  void OnSetParent(int32 parent_route_id,
-                   uint32 parent_texture_id,
-                   IPC::Message* reply_message);
+  void OnProduceFrontBuffer(const gpu::Mailbox& mailbox);
   void OnGetState(IPC::Message* reply_message);
   void OnGetStateFast(IPC::Message* reply_message);
   void OnAsyncFlush(int32 put_offset, uint32 flush_count);