mac: Make RWHVMac::ClearCompositorFrame clear locks

Ensure that the BrowserCompositorMac not hold on to a compositor lock
when requested to clear its compositor frame. This lock may be held
indefinitely (if the renderer hangs) and so the frame will never be
cleared.

Bug: 739621
Change-Id: I15d0e82bdf632f3379a48e959f198afb8a4ac218
Reviewed-on: https://chromium-review.googlesource.com/608239
Commit-Queue: ccameron chromium <ccameron@chromium.org>
Reviewed-by: Ken Buchanan <kenrb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#493563}
void DelegatedFrameHost::WasResized() {
  if (client_->DelegatedFrameHostDesiredSizeInDIP() !=
          current_frame_size_in_dip_ &&
      !client_->DelegatedFrameHostIsVisible())
    EvictDelegatedFrame();
  if (!resize_lock_ && !create_resize_lock_after_commit_)
    MaybeCreateResizeLock();
  UpdateGutters();
}

void DelegatedFrameHost::WasResized() {
  if (client_->DelegatedFrameHostDesiredSizeInDIP() !=
          current_frame_size_in_dip_ &&
      !client_->DelegatedFrameHostIsVisible())
    EvictDelegatedFrame();
  if (!resize_lock_ && !create_resize_lock_after_commit_)
    MaybeCreateResizeLock();
  UpdateGutters();
}
