Fix some unit_tests under PlzNavigate

content/test/test_render_frame_host.h

Index: content/test/test_render_frame_host.h
diff --git a/content/test/test_render_frame_host.h b/content/test/test_render_frame_host.h
index cd9b94f0119436202354c9791a5c7c910c5ddf50..70285ae417bc1b9adae94ec0b07f070aeadee2d4 100644
--- a/content/test/test_render_frame_host.h
+++ b/content/test/test_render_frame_host.h
@@ -63,6 +63,7 @@ class TestRenderFrameHost : public RenderFrameHostImpl,
   void SimulateNavigationError(const GURL& url, int error_code) override;
   void SimulateNavigationErrorPageCommit() override;
   void SimulateNavigationStop() override;
+  void SimulateUnloading() override;

[clamy, 2016/08/30 23:08:38]

I'm not a big fan of the name SimulateUnloading, since
a) we simulate BeforeUnload and not Unload
b) we simulate a lot more than that in the PlzNavigate case.

I don't have a good suggestion though. I've been thinking of
PrepareForCommitIfNecessary or SimulateCommitableState (which is what the
function is attempting to do) but that doesn't sound super good.

[scottmg, 2016/08/30 23:55:30]

I went with PrepareForCommitIfNecessary(). It's not pretty, but it's at least
explanatory I guess.

   void SendNavigate(int page_id,
                     int nav_entry_id,
                     bool did_create_new_entry,