Experiment to disable Prerendering with fast wind-down

chrome/browser/prerender/prerender_manager.h

Index: chrome/browser/prerender/prerender_manager.h
diff --git a/chrome/browser/prerender/prerender_manager.h b/chrome/browser/prerender/prerender_manager.h
index f95472655d929f4a1d0efb6b92b3900b36c94b8c..6c989097aee0c8d7793f2107f59d8e039d2ea692 100644
--- a/chrome/browser/prerender/prerender_manager.h
+++ b/chrome/browser/prerender/prerender_manager.h
@@ -207,6 +207,7 @@ class PrerenderManager : public base::SupportsWeakPtr<PrerenderManager>,
   static bool IsControlGroup();
   static bool IsNoUseGroup();
   static bool IsNoStatePrefetch();
+  bool IsPrerenderSilenceExperiment();
 
   // Query the list of current prerender pages to see if the given web contents
   // is prerendering a page. The optional parameter |origin| is an output
@@ -396,6 +397,9 @@ class PrerenderManager : public base::SupportsWeakPtr<PrerenderManager>,
   friend class PrerenderHandle;
   friend class UnitTestPrerenderManager;
 
+  // For testing |AddPrerender()| by iterating via a list of origins.
+  FRIEND_TEST_ALL_PREFIXES(PrerenderTest, PrerenderSilenceDisallowsNonOffline);

[mmenke, 2016/08/25 19:22:50]

I suggest adding a "IsPrerenderSilenceExperimentForTesting" method instead of
friending the test.  Makes what's exposed to tests clearer.

[pasko, 2016/08/26 11:22:12]

Hm, eliminating FRIEND_TEST_ALL_PREFIXES is indeed a good idea, and it seems you
are suggesting _not_ to call AddPrerender in the test (directly or indirectly).

I am hesitating, a simple wrapper AddPrerenderForTesting would allow testing
AddPrerender itself, and not just a method that it maybe-invokes.

OK, I've done what I think you mean, can revert/rework if it reveals more
problematic. PTAL.

+
   class OnCloseWebContentsDeleter;
   struct NavigationRecord;
   using PrerenderDataVector = std::vector<std::unique_ptr<PrerenderData>>;