Adds unit tests for offline_pages::PrerenderAdapter calling PrerenderManager.

chrome/browser/android/offline_pages/prerender_adapter.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_ANDROID_OFFLINE_PAGES_PRERENDER_ADAPTER_H_
 #define CHROME_BROWSER_ANDROID_OFFLINE_PAGES_PRERENDER_ADAPTER_H_
 
 #include <memory>
 
 #include "chrome/browser/prerender/prerender_handle.h"
@@ skipping 72 matching lines @@
 
   // Cancels any current prerendering operation and destroys its local handle.
   virtual void DestroyActive();
 
   // PrerenderHandle::Observer interface:
   void OnPrerenderStart(prerender::PrerenderHandle* handle) override;
   void OnPrerenderStopLoading(prerender::PrerenderHandle* handle) override;
   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.
   std::unique_ptr<prerender::PrerenderHandle> active_handle_;
 
   // 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);
 };
 
 }  // namespace offline_pages
 
 #endif  // CHROME_BROWSER_ANDROID_OFFLINE_PAGES_PRERENDER_ADAPTER_H_