[Smart Lock] Add UMA metrics to measure duration of unlock.

chrome/browser/signin/easy_unlock_service_signin_chromeos.h

Index: chrome/browser/signin/easy_unlock_service_signin_chromeos.h
diff --git a/chrome/browser/signin/easy_unlock_service_signin_chromeos.h b/chrome/browser/signin/easy_unlock_service_signin_chromeos.h
index eda7d7d96daf5ea9a79baa5f338c2eafaec61f6b..94b3cef951ee3d85c3239d409f759a07f1f29706 100644
--- a/chrome/browser/signin/easy_unlock_service_signin_chromeos.h
+++ b/chrome/browser/signin/easy_unlock_service_signin_chromeos.h
@@ -11,6 +11,7 @@
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
+#include "base/time/time.h"
 #include "base/values.h"
 #include "chrome/browser/chromeos/login/easy_unlock/easy_unlock_types.h"
 #include "chrome/browser/signin/easy_unlock_service.h"
@@ -82,6 +83,7 @@ class EasyUnlockServiceSignin : public EasyUnlockService,
   void ShutdownInternal() override;
   bool IsAllowedInternal() const override;
   void OnWillFinalizeUnlock(bool success) override;
+  void OnSuspendDone() override;
 
   // ScreenlockBridge::Observer implementation:
   void OnScreenDidLock(
@@ -123,6 +125,9 @@ class EasyUnlockServiceSignin : public EasyUnlockService,
   // shut down.
   bool service_active_;
 
+  // The timestamp for the most recent time when a user pod was focused.
+  base::TimeTicks user_pod_last_focused_timestamp_;
+
   base::WeakPtrFactory<EasyUnlockServiceSignin> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(EasyUnlockServiceSignin);