Limit prerender by only allowing one every X ms (X currently set to 500).

chrome/browser/prerender/prerender_manager.h

Index: chrome/browser/prerender/prerender_manager.h
diff --git a/chrome/browser/prerender/prerender_manager.h b/chrome/browser/prerender/prerender_manager.h
index fa53ae79abb3395633baf76926cf30513bda4845..44764b9df73b5d38dc8e5aaaa43b3cdde0e46644 100644
--- a/chrome/browser/prerender/prerender_manager.h
+++ b/chrome/browser/prerender/prerender_manager.h
@@ -102,6 +102,7 @@ class PrerenderManager : public base::RefCounted<PrerenderManager> {
 
   void SetPrerenderContentsFactory(
       PrerenderContents::Factory* prerender_contents_factory);
+  bool rate_limit_enabled_;
 
  private:
   // Test that needs needs access to internal functions.
@@ -122,6 +123,7 @@ class PrerenderManager : public base::RefCounted<PrerenderManager> {
   bool IsPrerenderElementFresh(const base::Time start) const;
   void DeleteOldEntries();
   virtual base::Time GetCurrentTime() const;
+  virtual base::TimeTicks GetCurrentTimeTicks() const;
   virtual PrerenderContents* CreatePrerenderContents(
       const GURL& url,
       const std::vector<GURL>& alias_urls,
@@ -136,6 +138,8 @@ class PrerenderManager : public base::RefCounted<PrerenderManager> {
 
   static void RecordPrefetchTagObservedOnUIThread();
 
+  bool DoesRateLimitAllowPrerender() const;
+
   Profile* profile_;
 
   base::TimeDelta max_prerender_age_;
@@ -160,6 +164,9 @@ class PrerenderManager : public base::RefCounted<PrerenderManager> {
   // Time interval at which periodic cleanups are performed.
   static const int kPeriodicCleanupIntervalMs = 1000;
 
+  // Time interval before a new prerender is allowed.
+  static const int kMinTimeBetweenPrerendersMs = 500;
+
   scoped_ptr<PrerenderContents::Factory> prerender_contents_factory_;
 
   static PrerenderManagerMode mode_;
@@ -174,6 +181,9 @@ class PrerenderManager : public base::RefCounted<PrerenderManager> {
   // pages.
   base::RepeatingTimer<PrerenderManager> repeating_timer_;
 
+  // Track time of last prerender to limit prerender spam.
+  base::TimeTicks last_prerender_start_time_;
+
   DISALLOW_COPY_AND_ASSIGN(PrerenderManager);
 };