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

chrome/browser/devtools/global_confirm_info_bar.cc

Index: chrome/browser/devtools/global_confirm_info_bar.cc
diff --git a/chrome/browser/devtools/global_confirm_info_bar.cc b/chrome/browser/devtools/global_confirm_info_bar.cc
index d25d08e904df81587d5684aa37fd39ff9b4816e0..9210099b15e7aa8fd6335390afaac20a4f54fb44 100644
--- a/chrome/browser/devtools/global_confirm_info_bar.cc
+++ b/chrome/browser/devtools/global_confirm_info_bar.cc
@@ -160,7 +160,10 @@ GlobalConfirmInfoBar::~GlobalConfirmInfoBar() {
   }
 }
 
-void GlobalConfirmInfoBar::TabInsertedAt(content::WebContents* web_contents,
+// Do not use |tab_strip_model| as it may be null from the call in
+// TabChangedAt().
+void GlobalConfirmInfoBar::TabInsertedAt(TabStripModel* tab_strip_model,
+                                         content::WebContents* web_contents,
                                          int index,
                                          bool foreground) {
   InfoBarService* infobar_service =
@@ -189,7 +192,7 @@ void GlobalConfirmInfoBar::TabChangedAt(content::WebContents* web_contents,
       InfoBarService::FromWebContents(web_contents);
   auto it = proxies_.find(infobar_service);
   if (it == proxies_.end())
-    TabInsertedAt(web_contents, index, false);
+    TabInsertedAt(nullptr, web_contents, index, false);
 }
 
 void GlobalConfirmInfoBar::OnInfoBarRemoved(infobars::InfoBar* info_bar,