Add UMA histogram for suppressed dialogs on prerender swap.

chrome/browser/prerender/prerender_manager.cc

 // Copyright (c) 2012 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 "chrome/browser/prerender/prerender_manager.h"
 
 #include <algorithm>
 #include <functional>
 #include <string>
 #include <vector>
@@ skipping 142 matching lines @@
 }  // namespace
 
 class PrerenderManager::OnCloseWebContentsDeleter
     : public content::WebContentsDelegate,
       public base::SupportsWeakPtr<
           PrerenderManager::OnCloseWebContentsDeleter> {
  public:
   OnCloseWebContentsDeleter(PrerenderManager* manager,
                             WebContents* tab)
       : manager_(manager),
-        tab_(tab) {
+        tab_(tab),
+        suppressed_dialog_(false) {
     tab_->SetDelegate(this);
     base::MessageLoop::current()->PostDelayedTask(FROM_HERE,
         base::Bind(&OnCloseWebContentsDeleter::ScheduleWebContentsForDeletion,
                    AsWeakPtr(), true),
         base::TimeDelta::FromSeconds(kDeleteWithExtremePrejudiceSeconds));
   }
 
   virtual void CloseContents(WebContents* source) OVERRIDE {
     DCHECK_EQ(tab_, source);
     ScheduleWebContentsForDeletion(false);
   }
 
   virtual void SwappedOut(WebContents* source) OVERRIDE {
     DCHECK_EQ(tab_, source);
     ScheduleWebContentsForDeletion(false);
   }
 
   virtual bool ShouldSuppressDialogs() OVERRIDE {
+    // Use this as a proxy for getting statistics on how often we fail to honor
+    // the beforeunload event.
+    suppressed_dialog_ = true;
     return true;
   }
 
  private:
   static const int kDeleteWithExtremePrejudiceSeconds = 3;
 
   void ScheduleWebContentsForDeletion(bool timeout) {
+    UMA_HISTOGRAM_BOOLEAN("Prerender.TabContentsDeleterTimeout", timeout);
+    UMA_HISTOGRAM_BOOLEAN("Prerender.TabContentsDeleterSuppressedDialog",
+                          suppressed_dialog_);
     tab_->SetDelegate(NULL);
     manager_->ScheduleDeleteOldWebContents(tab_.release(), this);
-    UMA_HISTOGRAM_BOOLEAN("Prerender.TabContentsDeleterTimeout", timeout);
+    // |this| is deleted at this point.
   }
 
   PrerenderManager* manager_;
   scoped_ptr<WebContents> tab_;
+  bool suppressed_dialog_;
 
   DISALLOW_COPY_AND_ASSIGN(OnCloseWebContentsDeleter);
 };
 
 // static
 bool PrerenderManager::is_prefetch_enabled_ = false;
 
 // static
 int PrerenderManager::prerenders_per_session_count_ = 0;
 
@@ skipping 371 matching lines @@
   // Update PPLT metrics:
   // If the tab has finished loading, record a PPLT of 0.
   // If the tab is still loading, reset its start time to the current time.
   PrerenderTabHelper* prerender_tab_helper =
       PrerenderTabHelper::FromWebContents(new_web_contents);
   DCHECK(prerender_tab_helper != NULL);
   prerender_tab_helper->PrerenderSwappedIn();
 
   if (old_web_contents->NeedToFireBeforeUnload()) {
     // Schedule the delete to occur after the tab has run its unload handlers.
+    // TODO(davidben): Honor the beforeunload event. http://crbug.com/304932
     on_close_web_contents_deleters_.push_back(
         new OnCloseWebContentsDeleter(this, old_web_contents));
     old_web_contents->GetRenderViewHost()->
         FirePageBeforeUnload(false);
   } else {
     // No unload handler to run, so delete asap.
     ScheduleDeleteOldWebContents(old_web_contents, NULL);
   }
 
   // TODO(cbentzel): Should prerender_contents move to the pending delete
@@ skipping 982 matching lines @@
     logged_in_state_->erase(domain_key);
 }
 
 void PrerenderManager::LoggedInPredictorDataReceived(
     scoped_ptr<LoggedInStateMap> new_map) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   logged_in_state_.swap(new_map);
 }
 
 }  // namespace prerender