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 22675dc154b3a1cefc19160f6bd2fb7bc86c8c37..4d15e381e13e3f8f91f2f3d8e385a953c0e0b828 100644
--- a/chrome/browser/prerender/prerender_manager.h
+++ b/chrome/browser/prerender/prerender_manager.h
@@ -106,6 +106,7 @@ 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.
@@ -126,6 +127,7 @@ 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,
@@ -140,6 +142,8 @@ class PrerenderManager : public base::RefCounted<PrerenderManager> {
 
   static void RecordPrefetchTagObservedOnUIThread();
 
+  bool DoesRateLimitAllowPrerender() const;
+
   Profile* profile_;
 
   base::TimeDelta max_prerender_age_;
@@ -168,6 +172,9 @@ 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_;
@@ -182,6 +189,9 @@ 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);
 };