Handle interface to prerenders.

chrome/browser/prerender/prerender_contents.h

Index: chrome/browser/prerender/prerender_contents.h
diff --git a/chrome/browser/prerender/prerender_contents.h b/chrome/browser/prerender/prerender_contents.h
index 0e1f4988ba8c0b2deccd458cd7c08153ff205096..f598cc043d42c08baf406ec0568cc60672cc895e 100644
--- a/chrome/browser/prerender/prerender_contents.h
+++ b/chrome/browser/prerender/prerender_contents.h
@@ -37,6 +37,7 @@ class WebContents;
 
 namespace prerender {
 
+class PrerenderHandle;
 class PrerenderManager;
 class PrerenderRenderViewHostObserver;
 class PrerenderTracker;
@@ -66,6 +67,13 @@ class PrerenderContents : public content::NotificationObserver,
     DISALLOW_COPY_AND_ASSIGN(Factory);
   };
 
+  // Predicate functor used in maps to sort by load start time.
+  class LessThanByLoadStartTime {

[dominich, 2012/06/22 15:36:16]

public?

+   public:
+    bool operator() (const PrerenderContents* lhs,
+                     const PrerenderContents* rhs) const;
+  };
+
   // Information on pages that the prerendered page has tried to prerender.
   struct PendingPrerenderInfo;
   typedef std::list<PendingPrerenderInfo> PendingPrerenderList;
@@ -80,7 +88,7 @@ class PrerenderContents : public content::NotificationObserver,
     // MatchComplete.
     MATCH_COMPLETE_DEFAULT,
     // A prerender that used to be a regular prerender, but has since been
-    // replaced by a MatchComplete dummy.  Therefore, we will record this only
+    // replaced by a MatchComplete dummy. Therefore, we will record this only
     // for Match, but not for MatchComplete.
     MATCH_COMPLETE_REPLACED,
     // A prerender that is a MatchComplete dummy replacing a regular prerender.
@@ -95,6 +103,10 @@ class PrerenderContents : public content::NotificationObserver,
 
   virtual ~PrerenderContents();
 
+  // For MatchComplete correctness, create a dummy replacement prerender contents
+  // to stand in for this prerender contents that (which we are about to destroy).
+  PrerenderContents* CreateDummyReplacement() const;
+
   bool Init();
 
   static Factory* CreateFactory();
@@ -153,6 +165,10 @@ class PrerenderContents : public content::NotificationObserver,
   Origin origin() const { return origin_; }
   uint8 experiment_id() const { return experiment_id_; }
 
+  int client_count() const { return client_count_; }

[dominich, 2012/06/22 15:36:16]

naming nit: I don't know what a client is or what this count is counting.

+  void IncrementClientCount();
+  void DecrementClientCount();
+
   base::TimeTicks load_start_time() const { return load_start_time_; }
 
   // Indicates whether this prerendered page can be used for the provided
@@ -160,7 +176,9 @@ class PrerenderContents : public content::NotificationObserver,
   // set to the URL that is found as a match if it is provided.
   // TODO(gavinp,mmenke): Rework matching to be based on both the URL
   // and the session WebStorage.
-  bool MatchesURL(const GURL& url, GURL* matching_url) const;
+  bool Matches(
+      const GURL& url,
+      const content::SessionStorageNamespace* session_storage_namespace);
 
   void OnJSOutOfMemory();
   bool ShouldSuppressDialogs();
@@ -216,12 +234,13 @@ class PrerenderContents : public content::NotificationObserver,
   bool IsCrossSiteNavigationPending() const;
 
   // Adds a pending prerender to the list.
-  virtual void AddPendingPrerender(const GURL& url,
+  virtual void AddPendingPrerender(scoped_ptr<PrerenderHandle> prerender_handle,

[dominich, 2012/06/22 15:36:16]

I don't know why, but seeing a scoped_ptr<> passed in here is causing me to
quirk an eyebrow. I'll revert when I've examined the .cc.

+                                   const GURL& url,
                                    const content::Referrer& referrer,
                                    const gfx::Size& size);
 
   // Returns true if |url| corresponds to a pending prerender.
-  bool IsPendingEntry(const GURL& url) const;
+  bool IsPendingEntry(const PrerenderHandle* prerender_handle) const;

[dominich, 2012/06/22 15:36:16]

if |prerender_handle| can never be NULL, prefer passing a reference. Even
better, make PrerenderHandle have sensible copy semantics and pass-by-value. I
know that seems wrong, but when I see 'Handle' I expect something that can be
passed by value. YMMV.

 
   // Reissues any pending prerender requests from the prerendered page.  Also
   // clears the list of pending requests.
@@ -258,6 +277,11 @@ class PrerenderContents : public content::NotificationObserver,
 
   bool prerendering_has_started_;
 
+  // Time at which we started to load the URL.  This is used to compute
+  // the time elapsed from initiating a prerender until the time the
+  // (potentially only partially) prerendered page is shown to the user.

[dominich, 2012/06/22 15:36:16]

Is it not used to potentially expire stale prerendered pages?

+  base::TimeTicks load_start_time_;

[dominich, 2012/06/22 15:36:16]

 The move to protected is unexpected as I thought PrerenderContents was a leaf
class. Unless this is exposed for tests?

+
  private:
   class TabContentsDelegateImpl;
 
@@ -306,6 +330,10 @@ class PrerenderContents : public content::NotificationObserver,
   // such as HTTP redirects or javascript redirects.
   std::vector<GURL> alias_urls_;
 
+  // Number of distinct clients of this prerendered page (distinct link elements
+  // for instance).

[dominich, 2012/06/22 15:36:16]

Ah - maybe instance_count_ ?

+  int client_count_;
+
   bool has_stopped_loading_;
 
   // True when the main frame has finished loading.
@@ -324,11 +352,6 @@ class PrerenderContents : public content::NotificationObserver,
   // Used solely to prevent double deletion.
   bool prerendering_has_been_cancelled_;
 
-  // Time at which we started to load the URL.  This is used to compute
-  // the time elapsed from initiating a prerender until the time the
-  // (potentially only partially) prerendered page is shown to the user.
-  base::TimeTicks load_start_time_;
-
   // Process Metrics of the render process associated with the
   // RenderViewHost for this object.
   scoped_ptr<base::ProcessMetrics> process_metrics_;