Backfill some UI tests.

content/public/test/test_renderer_host.cc

Index: content/public/test/test_renderer_host.cc
diff --git a/content/public/test/test_renderer_host.cc b/content/public/test/test_renderer_host.cc
index 538a2ccbff5ccb373e97f3fe458e113df2f68736..e30fb96b4568bc89a14c92e125e7543f207527d3 100644
--- a/content/public/test/test_renderer_host.cc
+++ b/content/public/test/test_renderer_host.cc
@@ -281,6 +281,11 @@ void RenderViewHostTestHarness::SetUp() {
   browser_context_.reset(CreateBrowserContext());
 
   SetContents(CreateTestWebContents());
+#if defined(USE_AURA)
+  static_cast<content::TestRenderWidgetHostView*>(
+      web_contents()->GetRenderWidgetHostView())
+      ->set_native_view(aura_test_helper_->root_window());

[sky, 2017/05/07 22:44:23]

This is confusing as you're setting the aura::Window created by AuraTestHelper
as the native view of the RenderWidgetHostView. My initial reaction is doing
that is confusing and easily misused. What about creating an aura::Window and
having TestRenderViewHost own it? You could parent the window to
AuraTestHelper's window if necessary.

[Bret, 2017/05/09 23:44:42]

Okay I made TestRenderWidgetHostView a WindowDelegate and it creates its own
Window, and that works. I guess it's not important that the Window actually does
anything, just that it exists.

+#endif
 
   if (IsBrowserSideNavigationEnabled())
     BrowserSideNavigationSetUp();