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::OnRenderProcessGone(int status, int exit_code) {
  if (!owned_by_render_frame_host_) {
    Destroy(true);
  } else {
    RendererExited(static_cast<base::TerminationStatus>(status), exit_code);
  }
}

void RenderWidgetHostImpl::OnRenderProcessGone(int status, int exit_code) {
  if (!owned_by_render_frame_host_) {
    Destroy(true);
  } else {
    RendererExited(static_cast<base::TerminationStatus>(status), exit_code);
  }
}
