Make unload tests stable.

content/browser/renderer_host/render_widget_host_impl.cc

Index: content/browser/renderer_host/render_widget_host_impl.cc
diff --git a/content/browser/renderer_host/render_widget_host_impl.cc b/content/browser/renderer_host/render_widget_host_impl.cc
index c7d44adae24d9862337c5d78da6578b7a523cb34..8c0e8edb4dbf25b06a4fc4168dc439984733a374 100644
--- a/content/browser/renderer_host/render_widget_host_impl.cc
+++ b/content/browser/renderer_host/render_widget_host_impl.cc
@@ -915,6 +915,11 @@ void RenderWidgetHostImpl::RestartHangMonitorTimeout() {
     hang_monitor_timeout_->Restart(hung_renderer_delay_);
 }
 
+void RenderWidgetHostImpl::DisableHangMonitorForTest() {
+  StopHangMonitorTimeout();
+  hang_monitor_timeout_.reset();

[Charlie Reis, 2016/05/23 17:03:30]

Yeah, I think this should be sufficient for this test.  We also have
RenderFrameHostImpl::DisableSwapOutTimerForTesting, but I don't think that's
necessary here because the swapout/unload event won't ever show dialogs.

nit: Maybe change the name from ForTest() to ForTesting() to be consistent (and
since there's a lot more of the latter in the codebase).

+}
+
 void RenderWidgetHostImpl::StopHangMonitorTimeout() {
   if (hang_monitor_timeout_)
     hang_monitor_timeout_->Stop();