Pepper takes ownership of a mailbox before passing it to the texture layer.

gpu/ipc/common/gpu_messages.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Multiply-included message file, hence no include guard here, but see below
 // for a much smaller-than-usual include guard section.
 
 #include <stdint.h>
 
 #include <string>
@@ skipping 119 matching lines @@
 // calling process.
 IPC_SYNC_MESSAGE_ROUTED1_2(GpuCommandBufferMsg_Initialize,
                            base::SharedMemoryHandle /* shared_state */,
                            bool /* result */,
                            gpu::Capabilities /* capabilities */)
 
 // Sets the shared memory buffer used for commands.
 IPC_SYNC_MESSAGE_ROUTED1_0(GpuCommandBufferMsg_SetGetBuffer,
                            int32_t /* shm_id */)
 
-// Produces the front buffer into a mailbox. This allows another context to draw
+// Takes the front buffer into a mailbox. This allows another context to draw
 // the output of this context.
-IPC_MESSAGE_ROUTED1(GpuCommandBufferMsg_ProduceFrontBuffer,
+IPC_MESSAGE_ROUTED1(GpuCommandBufferMsg_TakeFrontBuffer,
                     gpu::Mailbox /* mailbox */)
 
+// Returns a front buffer taken with GpuCommandBufferMsg_TakeFrontBuffer. This
+// allows it to be reused.
+IPC_MESSAGE_ROUTED3(GpuCommandBufferMsg_ReturnFrontBuffer,
+                    gpu::Mailbox /* mailbox */,
+                    gpu::SyncToken /* sync_token */,
+                    bool /* is_lost */)
+
 // Wait until the token is in a specific range, inclusive.
 IPC_SYNC_MESSAGE_ROUTED2_1(GpuCommandBufferMsg_WaitForTokenInRange,
                            int32_t /* start */,
                            int32_t /* end */,
                            gpu::CommandBuffer::State /* state */)
 
 // Wait until the get offset is in a specific range, inclusive.
 IPC_SYNC_MESSAGE_ROUTED2_1(GpuCommandBufferMsg_WaitForGetOffsetInRange,
                            int32_t /* start */,
                            int32_t /* end */,
@@ skipping 58 matching lines @@
                     GpuCommandBufferMsg_CreateImage_Params /* params */)
 
 // Destroy a previously created image.
 IPC_MESSAGE_ROUTED1(GpuCommandBufferMsg_DestroyImage, int32_t /* id */)
 
 // Attaches an external image stream to the client texture.
 IPC_SYNC_MESSAGE_ROUTED2_1(GpuCommandBufferMsg_CreateStreamTexture,
                            uint32_t, /* client_texture_id */
                            int32_t,  /* stream_id */
                            bool /* succeeded */)