VideoCapture: more migration IPC-->mojo, part 6

content/browser/renderer_host/media/shared_memory_buffer_tracker.cc

 // Copyright 2016 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.
 
 #include "content/browser/renderer_host/media/shared_memory_buffer_tracker.h"
 
 #include "base/memory/ptr_util.h"
 #include "content/browser/renderer_host/media/shared_memory_buffer_handle.h"
 
 namespace content {
@@ skipping 20 matching lines @@
 }
 
 std::unique_ptr<media::VideoCaptureBufferHandle>
 SharedMemoryBufferTracker::GetBufferHandle() {
   return base::MakeUnique<SharedMemoryBufferHandle>(this);
 }
 
 bool SharedMemoryBufferTracker::ShareToProcess(
     base::ProcessHandle process_handle,
     base::SharedMemoryHandle* new_handle) {
-  return shared_memory_.ShareToProcess(process_handle, new_handle);
+  *new_handle = base::SharedMemory::DuplicateHandle(shared_memory_.handle());

[Ken Rockot(use gerrit already), 2016/10/19 05:24:18]

So it looks like ShareToProcess is ultimately only called
VideoCaptureBufferPoolImpl::ShareToProcess, which in turn is only called from
VideoCaptureController::DoNewBufferOnIOThread, and then you're only using
new_handle for Mojo IPC anyway.

Given that is is not actually "sharing" to a process anymore, and
SharedMemoryHandle lifetime management is really not clear (it does -not- own
the buffer object, so AFAICT this code is leaky if you don't wrap and send
new_handle somewhere), and the resulting handle is only used for Mojo IPC, can
you please just change SharedMemoryBufferTracker::ShareToProcess to something
better like:

  mojo::ScopedSharedBufferHandle
SharedBufferMemoryTracker::GetHandleForTransit() {
    return mojo::WrapSharedMemoryHandle(
        base::SharedMemory::DuplicateHandle(shared_memory_.handle()),
        ...);
  }

You no longer need a ProcessHandle argument, you can propagate the simpler
interface to VideoCaptureBufferPool, and you can use a safer scoped buffer
handle type provided by Mojo.

[mcasas, 2016/10/19 17:53:29]

All right! I was a bit shy to dig deeper in this CL 
because the changes will spread across a few more
files but your suggestion tipped the balance.
Done.

+  return true;
 }
 
 }  // namespace content