Add metrics to keep track of the tab activate/deactivate cycle

chrome/browser/ui/cocoa/tabs/tab_strip_model_observer_bridge.mm

 // 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/ui/cocoa/tabs/tab_strip_model_observer_bridge.h"
 
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 
 using content::WebContents;
 
 TabStripModelObserverBridge::TabStripModelObserverBridge(TabStripModel* model,
                                                          id controller)
     : controller_(controller), model_(model) {
   DCHECK(model && controller);
   // Register to be a listener on the model so we can get updates and tell
   // |controller_| about them in the future.
   model_->AddObserver(this);
 }
 
 TabStripModelObserverBridge::~TabStripModelObserverBridge() {
   // Remove ourselves from receiving notifications.
   model_->RemoveObserver(this);
 }
 
-void TabStripModelObserverBridge::TabInsertedAt(WebContents* contents,
+void TabStripModelObserverBridge::TabInsertedAt(TabStripModel* tab_strip_model,
+                                                WebContents* contents,
                                                 int index,
                                                 bool foreground) {
   if ([controller_ respondsToSelector:
           @selector(insertTabWithContents:atIndex:inForeground:)]) {
     [controller_ insertTabWithContents:contents
                                atIndex:index
                           inForeground:foreground];
   }
 }
 
@@ skipping 69 matching lines @@
   if ([controller_ respondsToSelector:
           @selector(tabReplacedWithContents:previousContents:atIndex:)]) {
     [controller_ tabReplacedWithContents:new_contents
                         previousContents:old_contents
                                  atIndex:index];
   } else {
     TabChangedAt(new_contents, index, ALL);
   }
 }
 
-void TabStripModelObserverBridge::TabPinnedStateChanged(WebContents* contents,
-                                                        int index) {
+void TabStripModelObserverBridge::TabPinnedStateChanged(
+    TabStripModel* tab_strip_model,
+    WebContents* contents,
+    int index) {
   if ([controller_ respondsToSelector:
           @selector(tabPinnedStateChangedWithContents:atIndex:)]) {
     [controller_ tabPinnedStateChangedWithContents:contents
                                            atIndex:index];
   }
 }
 
 void TabStripModelObserverBridge::TabStripEmpty() {
   if ([controller_ respondsToSelector:@selector(tabStripEmpty)])
     [controller_ tabStripEmpty];
 }