Add UMA histograms for data usage tab model

chrome/browser/android/data_usage/data_use_tab_model.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_ANDROID_DATA_USAGE_DATA_USE_TAB_MODEL_H_
 #define CHROME_BROWSER_ANDROID_DATA_USAGE_DATA_USE_TAB_MODEL_H_
 
 #include <stdint.h>
 
 #include <string>
 
 #include "base/containers/hash_tables.h"
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 #include "base/observer_list_threadsafe.h"
 #include "base/threading/thread_checker.h"
+#include "base/time/time.h"
 #include "chrome/browser/android/data_usage/tab_data_use_entry.h"
 #include "components/data_usage/core/data_use.h"
 #include "url/gurl.h"
 
 namespace chrome {
 
 namespace android {
 
 class ExternalDataUseObserver;
 
@@ skipping 41 matching lines @@
     // Notification callback when tab tracking sessions are started and ended.
     // The callback will be received on the same thread AddObserver was called
     // from.
     virtual void NotifyTrackingStarting(int32_t tab_id) = 0;
     virtual void NotifyTrackingEnding(int32_t tab_id) = 0;
   };
 
   DataUseTabModel(const ExternalDataUseObserver* data_use_observer,
                   scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner);
 
-  ~DataUseTabModel();
+  virtual ~DataUseTabModel();
 
   base::WeakPtr<DataUseTabModel> GetWeakPtr();
 
   // Notifies the DataUseTabModel of navigation events. |tab_id| is the source
   // tab of the generated event, |transition| indicates the type of the UI
   // event/transition,  |url| is the URL in the source tab, |package| indicates
   // the android package name of external application that initiated the event.
   void OnNavigationEvent(int32_t tab_id,
                          TransitionType transition,
                          const GURL& url,
@@ skipping 12 matching lines @@
                           std::string* output_label) const;
 
   // Adds or removes observers from the observer list. These functions are
   // thread-safe and can be called from any thread.
   void AddObserver(TabDataUseObserver* observer);
   void RemoveObserver(TabDataUseObserver* observer);
 
  private:
   friend class DataUseTabModelTest;
   friend class MockTabDataUseEntryTest;
-  FRIEND_TEST_ALL_PREFIXES(DataUseTabModelTest, SingleTabTracking);
-  FRIEND_TEST_ALL_PREFIXES(DataUseTabModelTest, MultipleTabTracking);
-  FRIEND_TEST_ALL_PREFIXES(DataUseTabModelTest, ObserverStartEndEvents);
-  FRIEND_TEST_ALL_PREFIXES(DataUseTabModelTest, ObserverNotNotifiedAfterRemove);
-  FRIEND_TEST_ALL_PREFIXES(DataUseTabModelTest,
-                           MultipleObserverMultipleStartEndEvents);
   FRIEND_TEST_ALL_PREFIXES(DataUseTabModelTest, TabCloseEvent);
   FRIEND_TEST_ALL_PREFIXES(DataUseTabModelTest, TabCloseEventEndsTracking);
   FRIEND_TEST_ALL_PREFIXES(DataUseTabModelTest,
                            CompactTabEntriesWithinMaxLimit);
+  FRIEND_TEST_ALL_PREFIXES(DataUseTabModelTest,
+                           UnexpiredTabEntryRemovaltimeHistogram);
+  FRIEND_TEST_ALL_PREFIXES(DataUseTabModelTest,
+                           ExpiredInactiveTabEntryRemovaltimeHistogram);
+  FRIEND_TEST_ALL_PREFIXES(DataUseTabModelTest,
+                           ExpiredActiveTabEntryRemovaltimeHistogram);
 
   typedef base::hash_map<int32_t, TabDataUseEntry> TabEntryMap;
 
+  // Virtualized for unit test support.
+  virtual base::TimeTicks Now() const;
+
   // Returns the maximum number of tab entries to maintain session information
   // about.
   static size_t GetMaxTabEntriesForTests();
 
   // Notifies the observers that a data usage tracking session started for
   // |tab_id|.
   void NotifyObserversOfTrackingStarting(int32_t tab_id);
 
   // Notifies the observers that an active data usage tracking session ended for
   // |tab_id|.
@@ skipping 29 matching lines @@
   base::WeakPtrFactory<DataUseTabModel> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(DataUseTabModel);
 };
 
 }  // namespace android
 
 }  // namespace chrome
 
 #endif  // CHROME_BROWSER_ANDROID_DATA_USAGE_DATA_USE_TAB_MODEL_H_