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

content/browser/renderer_host/media/shared_memory_buffer_tracker.cc

Index: content/browser/renderer_host/media/shared_memory_buffer_tracker.cc
diff --git a/content/browser/renderer_host/media/shared_memory_buffer_tracker.cc b/content/browser/renderer_host/media/shared_memory_buffer_tracker.cc
index bf8e3cd47869215972d1277ae29fbdbd23375cb3..797fb224c783a5bde776e80d4560de1bc18687f5 100644
--- a/content/browser/renderer_host/media/shared_memory_buffer_tracker.cc
+++ b/content/browser/renderer_host/media/shared_memory_buffer_tracker.cc
@@ -38,7 +38,8 @@ SharedMemoryBufferTracker::GetBufferHandle() {
 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