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
void GpuCommandBufferStub::RemoveDestructionObserver(
    DestructionObserver* observer) {
  destruction_observers_.RemoveObserver(observer);
}

void GpuCommandBufferStub::RemoveDestructionObserver(
    DestructionObserver* observer) {
  destruction_observers_.RemoveObserver(observer);
}
