[TabManager] Unit tests to make sure of the number of times tabs can be discarded.

chrome/browser/memory/tab_manager.h

 // Copyright (c) 2012 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_MEMORY_TAB_MANAGER_H_
 #define CHROME_BROWSER_MEMORY_TAB_MANAGER_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 104 matching lines @@
 
   // Used to set the test TickClock, which then gets used by NowTicks(). See
   // |test_tick_clock_| for more details.
   void set_test_tick_clock(base::TickClock* test_tick_clock);
 
   // Returns the list of the stats for all renderers. Must be called on the UI
   // thread.
   TabStatsList GetUnsortedTabStats();
 
  private:
+  FRIEND_TEST_ALL_PREFIXES(TabManagerTest, CanOnlyDiscardOnce);
   FRIEND_TEST_ALL_PREFIXES(TabManagerTest, ChildProcessNotifications);
   FRIEND_TEST_ALL_PREFIXES(TabManagerTest, Comparator);
   FRIEND_TEST_ALL_PREFIXES(TabManagerTest, DiscardedTabKeepsLastActiveTime);
   FRIEND_TEST_ALL_PREFIXES(TabManagerTest, DiscardWebContentsAt);
   FRIEND_TEST_ALL_PREFIXES(TabManagerTest, InvalidOrEmptyURL);
   FRIEND_TEST_ALL_PREFIXES(TabManagerTest, IsInternalPage);
   FRIEND_TEST_ALL_PREFIXES(TabManagerTest, OomPressureListener);
   FRIEND_TEST_ALL_PREFIXES(TabManagerTest, ProtectPDFPages);
   FRIEND_TEST_ALL_PREFIXES(TabManagerTest, ProtectRecentlyUsedTabs);
   FRIEND_TEST_ALL_PREFIXES(TabManagerTest, ProtectVideoTabs);
@@ skipping 194 matching lines @@
 
   // Weak pointer factory used for posting delayed tasks to task_runner_.
   base::WeakPtrFactory<TabManager> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(TabManager);
 };
 
 }  // namespace memory
 
 #endif  // CHROME_BROWSER_MEMORY_TAB_MANAGER_H_