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

chrome/browser/signin/easy_unlock_service_regular.h

Index: chrome/browser/signin/easy_unlock_service_regular.h
diff --git a/chrome/browser/signin/easy_unlock_service_regular.h b/chrome/browser/signin/easy_unlock_service_regular.h
index 6b34afef928865ae1645806a167e58b3ba03188d..324d234c9cdebd946e6c42133934d86d021f14ae 100644
--- a/chrome/browser/signin/easy_unlock_service_regular.h
+++ b/chrome/browser/signin/easy_unlock_service_regular.h
@@ -11,6 +11,7 @@
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/prefs/pref_change_registrar.h"
+#include "base/time/time.h"
 #include "chrome/browser/signin/easy_unlock_service.h"
 #include "chrome/browser/signin/screenlock_bridge.h"
 
@@ -67,6 +68,7 @@ class EasyUnlockServiceRegular : public EasyUnlockService,
   void ShutdownInternal() override;
   bool IsAllowedInternal() const override;
   void OnWillFinalizeUnlock(bool success) override;
+  void OnSuspendDone() override;
 
   // ScreenlockBridge::Observer implementation:
   void OnScreenDidLock(
@@ -75,6 +77,7 @@ class EasyUnlockServiceRegular : public EasyUnlockService,
       ScreenlockBridge::LockHandler::ScreenType screen_type) override;
   void OnFocusedUserChanged(const std::string& user_id) override;
 
+
   // Callback when the controlling pref changes.
   void OnPrefsChanged();
 
@@ -116,6 +119,12 @@ class EasyUnlockServiceRegular : public EasyUnlockService,
   // password-based unlocks for metrics.
   bool will_unlock_using_easy_unlock_;
 
+  // The timestamp for the most recent time when the lock screen was shown. The
+  // lock screen is typically shown when the user awakens her computer from
+  // sleep -- e.g. by opening the lid -- but can also be shown if the screen is
+  // locked but the computer does not go to sleep.
+  base::TimeTicks lock_screen_last_shown_timestamp_;
+
   base::WeakPtrFactory<EasyUnlockServiceRegular> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(EasyUnlockServiceRegular);