Add perf histogram and tests for inline signin

chrome/browser/ui/webui/signin/inline_login_handler.h

Index: chrome/browser/ui/webui/signin/inline_login_handler.h
diff --git a/chrome/browser/ui/webui/signin/inline_login_handler.h b/chrome/browser/ui/webui/signin/inline_login_handler.h
index b3650fb6a195efc8111bdad7a44e2a9ce3cc04e6..5772ddd784247c9fb7f243734aa6a985cabfbfc2 100644
--- a/chrome/browser/ui/webui/signin/inline_login_handler.h
+++ b/chrome/browser/ui/webui/signin/inline_login_handler.h
@@ -5,6 +5,7 @@
 #ifndef CHROME_BROWSER_UI_WEBUI_SIGNIN_INLINE_LOGIN_HANDLER_H_
 #define CHROME_BROWSER_UI_WEBUI_SIGNIN_INLINE_LOGIN_HANDLER_H_
 
+#include "base/time/time.h"
 #include "content/public/browser/web_ui_message_handler.h"
 
 // The base class handler for the inline login WebUI.
@@ -29,6 +30,9 @@ class InlineLoginHandler : public content::WebUIMessageHandler {
   // JS callback to initialize the gaia auth extension. It calls
   // |SetExtraInitParams| to set extra init params.
   void HandleInitializeMessage(const base::ListValue* args);
+  // JS callback triggered when the gaia extension (and the embedded gaia
+  // webview if applicable) has completed loading.
+  void HandleLoginUIInitializedMessage(const base::ListValue* args);
   // JS callback to complete login. It calls |CompleteLogin| to do the real
   // work.
   void HandleCompleteLoginMessage(const base::ListValue* args);
@@ -36,6 +40,8 @@ class InlineLoginHandler : public content::WebUIMessageHandler {
   virtual void SetExtraInitParams(base::DictionaryValue& params) {}
   virtual void CompleteLogin(const base::ListValue* args) = 0;
 
+  base::Time load_start_time_;
+
   DISALLOW_COPY_AND_ASSIGN(InlineLoginHandler);
 };