[Prerender] Add a "SimpleLoad" mode to be used as a comparison reference

chrome/browser/prerender/prerender_manager.h

 // Copyright (c) 2012 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_PRERENDER_PRERENDER_MANAGER_H_
 #define CHROME_BROWSER_PRERENDER_PRERENDER_MANAGER_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 65 matching lines @@
 // views of web pages. All methods must be called on the UI thread unless
 // indicated otherwise.
 class PrerenderManager : public content::NotificationObserver,
                          public content::RenderProcessHostObserver,
                          public KeyedService,
                          public MediaCaptureDevicesDispatcher::Observer {
  public:
   enum PrerenderManagerMode {
     PRERENDER_MODE_DISABLED,
     PRERENDER_MODE_ENABLED,
-    PRERENDER_MODE_NOSTATE_PREFETCH
+    PRERENDER_MODE_NOSTATE_PREFETCH,
+    // Like PRERENDER_MODE_DISABLED, but keeps track of pages that would have
+    // been prerendered and records metrics for comparison with other modes.
+    PRERENDER_MODE_SIMPLE_LOAD_EXPERIMENT
   };
 
   // One or more of these flags must be passed to ClearData() to specify just
   // what data to clear.  See function declaration for more information.
   enum ClearFlags {
     CLEAR_PRERENDER_CONTENTS = 0x1 << 0,
     CLEAR_PRERENDER_HISTORY = 0x1 << 1,
     CLEAR_MAX = 0x1 << 2
   };
 
@@ skipping 118 matching lines @@
   // |is_no_store| must be true if the main resource has a "no-store" cache
   // control HTTP header.
   void RecordFirstContentfulPaint(const GURL& url,
                                   bool is_no_store,
                                   base::TimeDelta time);
 
   static PrerenderManagerMode GetMode();
   static void SetMode(PrerenderManagerMode mode);
   static bool IsPrerenderingPossible();
   static bool IsNoStatePrefetch();
+  static bool IsSimpleLoadExperiment();
 
   // 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
   // parameter which, if a prerender is found, is set to the Origin of the
   // prerender |web_contents|.
   bool IsWebContentsPrerendering(const content::WebContents* web_contents,
                                  Origin* origin) const;
 
   // Whether the PrerenderManager has an active prerender with the given url and
   // SessionStorageNamespace associated with the given WebContents.
@@ skipping 366 matching lines @@
   std::unique_ptr<base::TickClock> tick_clock_;
 
   base::WeakPtrFactory<PrerenderManager> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(PrerenderManager);
 };
 
 }  // namespace prerender
 
 #endif  // CHROME_BROWSER_PRERENDER_PRERENDER_MANAGER_H_