Implementing TabManager extensions API Discard Function.

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 86 matching lines @@
   // the automatic tab discarding mechanism. Note that this is not used when
   // discarding a particular tab from about:discards.
   bool CanDiscardTab(int64_t target_web_contents_id) const;
 
   // Discards a tab to free the memory occupied by its renderer. The tab still
   // exists in the tab-strip; clicking on it will reload it.
   void DiscardTab();
 
   // Discards a tab with the given unique ID. The tab still exists in the
   // tab-strip; clicking on it will reload it. Returns null if the tab cannot
-  // be found or cannot be discarded. Otherwise returns the old web_contents
-  // that got discarded. This value is mostly useful during testing.
+  // be found or cannot be discarded. Otherwise returns the new web_contents
+  // of the discarded tab.
   content::WebContents* DiscardTabById(int64_t target_web_contents_id);
 
+  // Method used by the extensions API to discard tabs. If |contents| is null,
+  // discards the least important tab using DiscardTab(). Otherwise discards
+  // the given contents. Returns the new web_contents or null if no tab
+  // was discarded.
+  content::WebContents* DiscardTabByExtension(content::WebContents* contents);
+
   // Log memory statistics for the running processes, then discards a tab.
   // Tab discard happens sometime later, as collecting the statistics touches
   // multiple threads and takes time.
   void LogMemoryAndDiscardTab();
 
   // Log memory statistics for the running processes, then call the callback.
   void LogMemory(const std::string& title, const base::Closure& callback);
 
   // 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();
 
   void AddObserver(TabManagerObserver* observer);
   void RemoveObserver(TabManagerObserver* observer);
 
+  // Used in tests to change the protection time of the tabs.
+  void set_minimum_protection_time_for_tests(
+      base::TimeDelta minimum_protection_time);
+
   // Returns the auto-discardable state of the tab. When true, the tab is
   // eligible to be automatically discarded when critical memory pressure hits,
   // otherwise the tab is ignored and will never be automatically discarded.
   // Note that this property doesn't block the discarding of the tab via other
   // methods (about:discards for instance).
   bool IsTabAutoDiscardable(content::WebContents* contents) const;
 
   // Sets/clears the auto-discardable state of the tab.
   void SetTabAutoDiscardableState(content::WebContents* contents, bool state);
 
@@ skipping 124 matching lines @@
   WebContentsData* GetWebContentsData(content::WebContents* contents) const;
 
   // Returns either the system's clock or the test clock. See |test_tick_clock_|
   // for more details.
   base::TimeTicks NowTicks() const;
 
   // Dispatches a memory pressure message to a single child process, and
   // schedules another call to itself as long as memory pressure continues.
   void DoChildProcessDispatch();
 
-  // Implementation of DiscardTab.
-  bool DiscardTabImpl();
+  // Implementation of DiscardTab. Returns null if no tab was discarded.
+  // Otherwise returns the new web_contents of the discarded tab.
+  content::WebContents* DiscardTabImpl();
 
   // Returns true if tabs can be discarded only once.
   bool CanOnlyDiscardOnce();
 
   // Timer to periodically update the stats of the renderers.
   base::RepeatingTimer update_timer_;
 
   // Timer to periodically report whether a tab has been discarded since the
   // last time the timer has fired.
   base::RepeatingTimer recent_tab_discard_timer_;
@@ skipping 77 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_