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

chrome/browser/memory/tab_manager.cc

Index: chrome/browser/memory/tab_manager.cc
diff --git a/chrome/browser/memory/tab_manager.cc b/chrome/browser/memory/tab_manager.cc
index fc69c65b67e0231bf2ec7350f2eeaa7bb457849f..b2b4b04714532a84c0510a2cdba1bb8183432f70 100644
--- a/chrome/browser/memory/tab_manager.cc
+++ b/chrome/browser/memory/tab_manager.cc
@@ -798,7 +798,8 @@ void TabManager::ActiveTabChanged(content::WebContents* old_contents,
     GetWebContentsData(old_contents)->SetLastInactiveTime(NowTicks());
 }
 
-void TabManager::TabInsertedAt(content::WebContents* contents,
+void TabManager::TabInsertedAt(TabStripModel* tab_strip_model,
+                               content::WebContents* contents,
                                int index,
                                bool foreground) {
   // Only interested in background tabs, as foreground tabs get taken care of by