Add UMA to measure potential impact of Fast Tab Close.

content/browser/web_contents/web_contents_impl.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 "content/browser/web_contents/web_contents_impl.h"
 
 #include <utility>
 
 #include "base/command_line.h"
 #include "base/metrics/histogram.h"
@@ skipping 372 matching lines @@
   // NULL if this contents was part of a window that closed.
   if (GetNativeView()) {
     RenderViewHost* host = GetRenderViewHost();
     if (host && host->GetView())
       RenderWidgetHostViewPort::FromRWHV(host->GetView())->WillWmDestroy();
   }
 #endif
 
   // OnCloseStarted isn't called in unit tests.
   if (!close_start_time_.is_null()) {
-    UMA_HISTOGRAM_TIMES("Tab.Close",
-        base::TimeTicks::Now() - close_start_time_);
+    base::TimeTicks now = base::TimeTicks::Now();
+    base::TimeTicks unload_start_time = close_start_time_;
+    if (!before_unload_end_time_.is_null())
+      unload_start_time = before_unload_end_time_;
+    UMA_HISTOGRAM_TIMES("Tab.Close", now - close_start_time_);
+    UMA_HISTOGRAM_TIMES("Tab.Close.UnloadTime", now - unload_start_time);
   }
 
   FOR_EACH_OBSERVER(WebContentsObserver,
                     observers_,
                     WebContentsImplDestroyed());
 
   SetDelegate(NULL);
 }
 
 WebContentsImpl* WebContentsImpl::Create(
@@ skipping 2702 matching lines @@
         content::INVALIDATE_TYPE_LOAD | content::INVALIDATE_TYPE_TAB);
   }
 }
 
 void WebContentsImpl::WorkerCrashed() {
   if (delegate_)
     delegate_->WorkerCrashed(this);
 }
 
 void WebContentsImpl::BeforeUnloadFiredFromRenderManager(
-    bool proceed,
+    bool proceed, const base::TimeTicks& proceed_time,
     bool* proceed_to_fire_unload) {
+  before_unload_end_time_ = proceed_time;
   if (delegate_)
     delegate_->BeforeUnloadFired(this, proceed, proceed_to_fire_unload);
 }
 
 void WebContentsImpl::RenderViewGoneFromRenderManager(
     RenderViewHost* render_view_host) {
   DCHECK(crashed_status_ != base::TERMINATION_STATUS_STILL_RUNNING);
   RenderViewGone(render_view_host, crashed_status_, crashed_error_code_);
 }
 
@@ skipping 101 matching lines @@
                                      IPC::Message* reply_msg,
                                      bool success,
                                      const string16& user_input) {
   if (is_showing_before_unload_dialog_ && !success) {
     // If a beforeunload dialog is canceled, we need to stop the throbber from
     // spinning, since we forced it to start spinning in Navigate.
     DidStopLoading(rvh);
     controller_.DiscardNonCommittedEntries();
 
     close_start_time_ = base::TimeTicks();
+    before_unload_end_time_ = base::TimeTicks();
   }
   is_showing_before_unload_dialog_ = false;
   static_cast<RenderViewHostImpl*>(
       rvh)->JavaScriptDialogClosed(reply_msg, success, user_input);
 }
 
 void WebContentsImpl::SetEncoding(const std::string& encoding) {
   encoding_ = content::GetContentClient()->browser()->
       GetCanonicalEncodingNameByAliasName(encoding);
 }
@@ skipping 42 matching lines @@
       old_browser_plugin_host()->embedder_render_process_host();
   *embedder_container_id = old_browser_plugin_host()->instance_id();
   int embedder_process_id =
       embedder_render_process_host ? embedder_render_process_host->GetID() : -1;
   if (embedder_process_id != -1) {
     *embedder_channel_name =
         StringPrintf("%d.r%d", render_view_host->GetProcess()->GetID(),
                      embedder_process_id);
   }
 }