Allocate a FrameSinkId for RenderWidgetHostViewAura in mus+ash

RenderWidgetHostViewChildFrame expects its parent to have a valid
FrameSinkId. Make sure RenderWidgetHostViewAura has a FrameSinkId even
if DelegatedFrameHost is not used (in mus+ash).

BUG=706553
TBR=jam@chromium.org

Review-Url: https://codereview.chromium.org/2847253003
Cr-Commit-Position: refs/heads/master@{#468179}
void RenderWidgetHostViewAura::UpdateNeedsBeginFramesInternal() {
  if (!delegated_frame_host_)
    return;
  delegated_frame_host_->SetNeedsBeginFrames(needs_begin_frames_ ||
                                             needs_flush_input_);
}

void RenderWidgetHostViewAura::UpdateNeedsBeginFramesInternal() {
  if (!delegated_frame_host_)
    return;
  delegated_frame_host_->SetNeedsBeginFrames(needs_begin_frames_ ||
                                             needs_flush_input_);
}
