PlzNavigate: Speculatively spawns a renderer process for navigations.

content/public/test/web_contents_tester.h

Index: content/public/test/web_contents_tester.h
diff --git a/content/public/test/web_contents_tester.h b/content/public/test/web_contents_tester.h
index 24953ed9c258111a4428ac22d0fee1d09a4b2981..5a586319794a487bc5a8437458507571e5e3934f 100644
--- a/content/public/test/web_contents_tester.h
+++ b/content/public/test/web_contents_tester.h
@@ -64,6 +64,9 @@ class WebContentsTester {
   // current RenderFrameHost of the main frame, use WebContents::GetMainFrame().
   virtual RenderFrameHost* GetPendingMainFrame() const = 0;
 
+  // Gets the speculative RenderFrameHost, if any, for the main frame.

[clamy, 2014/12/19 13:35:57]

Please preface this with a PlzNavigate comment. Also, we would need a method
that would return either the pending RFH in current navigation or the
speculative one in PlzNavigate to use in unit tests (to replace
GetPendingMainFrame in many of them). Maybe it can be called GetNextMainFrame,
or GetFutureMainFrame.

And I'm not sure we currently need to expose both these methods to the public
API.

[nasko, 2014/12/20 00:09:09]

This definitely should not be exposed through public API. This is totally an
internal optimization in content/ and shouldn't be known outside of it (even
outside of RFHM if we want to be precise).

[carlosk, 2014/12/29 16:40:16]

I added it to the public API because there is already one for the pending RFH.
It's now removed from it.

Given the previous request from clamy@ I kept it in the private API, added the
pending-speculative shared getter but turned both into private methods.

+  virtual RenderFrameHost* GetSpeculativeMainFrame() const = 0;
+
   // Creates a pending navigation to the given URL with the default parameters
   // and then commits the load with a page ID one larger than any seen. This
   // emulates what happens on a new navigation.