Adds unit tests for offline_pages::PrerenderAdapter calling PrerenderManager.

chrome/browser/android/offline_pages/prerender_adapter.h

Index: chrome/browser/android/offline_pages/prerender_adapter.h
diff --git a/chrome/browser/android/offline_pages/prerender_adapter.h b/chrome/browser/android/offline_pages/prerender_adapter.h
index 1382170565df9b1bab5da23d274f07d8365de9e3..d675f8e2e612d4b2ef850781e814ac134f69465e 100644
--- a/chrome/browser/android/offline_pages/prerender_adapter.h
+++ b/chrome/browser/android/offline_pages/prerender_adapter.h
@@ -90,6 +90,10 @@ class PrerenderAdapter : public prerender::PrerenderHandle::Observer {
   void OnPrerenderDomContentLoaded(prerender::PrerenderHandle* handle) override;
   void OnPrerenderStop(prerender::PrerenderHandle* handle) override;
 
+  // Overrides the PrerenderManager for unit testing.
+  void SetPrerenderManagerForTest(
+      prerender::PrerenderManager* test_prerender_manager);
+
  private:
   // At most one prerender request may be active for this adapter and this
   // holds its handle if one is active.
@@ -98,6 +102,9 @@ class PrerenderAdapter : public prerender::PrerenderHandle::Observer {
   // Observer of active handle events. Not owned.
   PrerenderAdapter::Observer* observer_;
 
+  // Overridden PrerenderManager for unit tests. Not owned.
+  prerender::PrerenderManager* test_prerender_manager_;
+
   DISALLOW_COPY_AND_ASSIGN(PrerenderAdapter);
 };