Add observer interface to PrerenderContents.

chrome/browser/prerender/prerender_tracker.h

Index: chrome/browser/prerender/prerender_tracker.h
diff --git a/chrome/browser/prerender/prerender_tracker.h b/chrome/browser/prerender/prerender_tracker.h
index f4bc1088ec4faef8b36da6f930d2873417888059..95447b699e67ad925fefd487e3bc2b11b861b728 100644
--- a/chrome/browser/prerender/prerender_tracker.h
+++ b/chrome/browser/prerender/prerender_tracker.h
@@ -7,11 +7,13 @@
 
 #include <map>
 #include <set>
+#include <utility>
 #include <vector>
 
 #include "base/gtest_prod_util.h"
 #include "base/synchronization/lock.h"
 #include "base/threading/non_thread_safe.h"
+#include "chrome/browser/prerender/prerender_contents.h"
 #include "chrome/browser/prerender/prerender_final_status.h"
 #include "googleurl/src/gurl.h"
 
@@ -23,10 +25,13 @@ struct RenderViewInfo;
 // PrerenderTracker is responsible for keeping track of all prerendering
 // RenderViews and their statuses.  Its list is guaranteed to be up to date
 // and can be modified on any thread.
-class PrerenderTracker {
+class PrerenderTracker : public base::NonThreadSafe,
+                         public PrerenderContents::Observer {
  public:
   PrerenderTracker();
-  ~PrerenderTracker();
+  virtual ~PrerenderTracker();
+
+  void AddPrerenderContents(PrerenderContents* prerender_contents);
 
   // Attempts to set the status of the specified RenderViewHost to
   // FINAL_STATUS_USED.  Returns true on success.  Returns false if it has
@@ -83,13 +88,12 @@ class PrerenderTracker {
 
   // Must be called when a RenderView starts prerendering, before the first
   // navigation starts to avoid any races.
-  void OnPrerenderingStarted(int child_id, int route_id,
-                             PrerenderManager* prerender_manager);
+  virtual void OnPrerenderStart(PrerenderContents* prerender_contents) OVERRIDE;
 
   // Must be called when a RenderView stops prerendering, either because the
   // RenderView was used or prerendering was cancelled and it is being
   // destroyed.
-  void OnPrerenderingFinished(int child_id, int route_id);
+  virtual void OnPrerenderStop(PrerenderContents* prerender_contents) OVERRIDE;
 
   // Attempts to set the FinalStatus of the specified RenderView to
   // |desired_final_status|.  If non-NULL, |actual_final_status| is set to the
@@ -120,6 +124,10 @@ class PrerenderTracker {
 
   static PrerenderTracker* GetDefault();
 
+  // Set of prerender_contents being observed by this tracker. Can only access
+  // on UI thread.
+  std::set<prerender::PrerenderContents*> observing_set_;
+
   // |final_status_map_lock_| protects access to |final_status_map_|.
   mutable base::Lock final_status_map_lock_;
   // Map containing child/route id pairs and their final statuses.  Must only be