Convert plugin and GPU process to brokered handle duplication.

BUG=119250
Review URL: https://chromiumcodereview.appspot.com/9958034

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@132303 0039d316-1c4b-4281-b951-d872f2087c98
 GpuChannel::~GpuChannel() {
 }

 GpuChannel::~GpuChannel() {
#if defined(OS_WIN)
  if (renderer_process_)
    CloseHandle(renderer_process_);
#endif
 }
