Adds unit tests for offline_pages::PrerenderAdapter calling PrerenderManager.

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 9ed133e1e47da0f834547c3440cdc62306aa096c..510f10d321c97ccaaed6411837bb1fdf40aa900c 100644
--- a/chrome/browser/prerender/prerender_manager.h
+++ b/chrome/browser/prerender/prerender_manager.h
@@ -55,6 +55,10 @@ namespace gfx {
 class Size;
 }
 
+namespace offline_pages {
+class PrerenderAdapterTest;
+}
+
 namespace prerender {
 
 class PrerenderHandle;
@@ -394,6 +398,7 @@ class PrerenderManager : public base::SupportsWeakPtr<PrerenderManager>,
   friend class PrerenderContents;
   friend class PrerenderHandle;
   friend class UnitTestPrerenderManager;
+  friend class offline_pages::PrerenderAdapterTest;

[mmenke, 2016/06/11 00:40:32]

Is this still needed?  If so, I recommend adding BlahForTest[ing] methods
instead.  That gives a more defined API to deal with.  I know nothing else is
doing that, but IMHO, they should be.

[dougarnett, 2016/06/12 16:43:09]

SetPrerenderContentsFactory() is what the test needs access to (possibly all
that the ::InstantSearchPrerendererTest friend above needs too).

Looks like this is only used for browsertest and instantsearch test so options
might be to just make public named as is or make public and revise name to
*ForTest and change the callers. 

[mmenke, 2016/06/13 14:52:59]

Could you please rename it to SetPrerenderContentsFactoryForTest, and make it
public, and update all callers.

If that allows you to remove the friend declaration for
::InstantSearchPrerendererTest (Or anything else), please do so.

 
   class OnCloseWebContentsDeleter;
   struct NavigationRecord;