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

chrome/browser/prerender/prerender_manager_unittest.cc

 // Copyright (c) 2010 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.
 
 #include "base/time.h"
 #include "chrome/browser/prerender/prerender_contents.h"
 #include "chrome/browser/prerender/prerender_manager.h"
 #include "content/browser/browser_thread.h"
 #include "googleurl/src/gurl.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ skipping 36 matching lines @@
   bool has_started_;
   FinalStatus expected_final_status_;
 };
 
 class TestPrerenderManager : public PrerenderManager {
  public:
   TestPrerenderManager()
       : PrerenderManager(NULL),
         time_(base::Time::Now()),
         next_pc_(NULL) {
+    rate_limit_enabled_ = false;
   }
 
   void AdvanceTime(base::TimeDelta delta) {
     time_ += delta;
   }
 
   void SetNextPrerenderContents(PrerenderContents* pc) {
     next_pc_.reset(pc);
   }
 
@@ skipping 199 matching lines @@
   EXPECT_FALSE(prerender_manager_->AddSimplePreload(url));
   EXPECT_FALSE(prerender_manager_->AddSimplePreload(alias_url1));
   EXPECT_FALSE(prerender_manager_->AddSimplePreload(alias_url2));
   ASSERT_EQ(pc, prerender_manager_->GetEntry(url));
 
   pc->set_final_status(FINAL_STATUS_USED);
   delete pc;
 }
 
 }  // naemspace prerender