Check that RWHI isn't deleted manually while owned by a scoped_ptr in RVHI

BUG=590284

Review URL: https://codereview.chromium.org/1747183002

Cr-Commit-Position: refs/heads/master@{#378844}
void RenderWidgetHostImpl::ForwardEmulatedTouchEvent(
      const blink::WebTouchEvent& touch_event) {
  TRACE_EVENT0("input", "RenderWidgetHostImpl::ForwardEmulatedTouchEvent");

  TouchEventWithLatencyInfo touch_with_latency(touch_event);
  latency_tracker_.OnInputEvent(touch_event, &touch_with_latency.latency);
  input_router_->SendTouchEvent(touch_with_latency);
}

void RenderWidgetHostImpl::ForwardEmulatedTouchEvent(
      const blink::WebTouchEvent& touch_event) {
  TRACE_EVENT0("input", "RenderWidgetHostImpl::ForwardEmulatedTouchEvent");

  TouchEventWithLatencyInfo touch_with_latency(touch_event);
  latency_tracker_.OnInputEvent(touch_event, &touch_with_latency.latency);
  input_router_->SendTouchEvent(touch_with_latency);
}
