CrOS: Prefer discarding internal web UI pages when out of memory

chrome/browser/chromeos/memory/oom_priority_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_CHROMEOS_MEMORY_OOM_PRIORITY_MANAGER_H_
 #define CHROME_BROWSER_CHROMEOS_MEMORY_OOM_PRIORITY_MANAGER_H_
 
 #include <vector>
 
 #include "base/compiler_specific.h"
 #include "base/gtest_prod_util.h"
 #include "base/hash_tables.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/process.h"
 #include "base/string16.h"
 #include "base/synchronization/lock.h"
 #include "base/time.h"
 #include "base/timer.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 
+class GURL;
+
 namespace chromeos {
 
 class LowMemoryObserver;
 
 // The OomPriorityManager periodically checks (see
 // ADJUSTMENT_INTERVAL_SECONDS in the source) the status of renderers
 // and adjusts the out of memory (OOM) adjustment value (in
 // /proc/<pid>/oom_score_adj) of the renderers so that they match the
 // algorithm embedded here for priority in being killed upon OOM
 // conditions.
@@ skipping 20 matching lines @@
   // Returns true if it successfully found a tab and discarded it.
   bool DiscardTab();
 
   // 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();
 
  private:
   FRIEND_TEST_ALL_PREFIXES(OomPriorityManagerTest, Comparator);
+  FRIEND_TEST_ALL_PREFIXES(OomPriorityManagerTest, IsReloadableUI);
 
   struct TabStats {
     TabStats();
     ~TabStats();
     bool is_app;  // browser window is an app
+    bool is_reloadable_ui;  // Reloadable web UI page, like NTP or Settings.
     bool is_pinned;
     bool is_selected;  // selected in the currently active browser window
     bool is_discarded;
     base::TimeTicks last_selected;
     base::ProcessHandle renderer_handle;
     string16 title;
     int64 tab_contents_id;  // unique ID per WebContents
   };
   typedef std::vector<TabStats> TabStatsList;
 
+  // Returns true if the |url| represents an internal Chrome web UI page that
+  // can be easily reloaded and hence makes a good choice to discard.
+  static bool IsReloadableUI(const GURL& url);
+
   // Discards a tab with the given unique ID.  Returns true if discard occurred.
   bool DiscardTabById(int64 target_web_contents_id);
 
   // Records UMA histogram statistics for a tab discard. We record statistics
   // for user triggered discards via chrome://discards/ because that allows us
   // to manually test the system.
   void RecordDiscardStatistics();
 
   // Returns the number of tabs open in all browser instances.
   int GetTabCount() const;
@@ skipping 46 matching lines @@
 
   // Number of times we have discarded a tab, for statistics.
   int discard_count_;
 
   DISALLOW_COPY_AND_ASSIGN(OomPriorityManager);
 };
 
 }  // namespace chrome
 
 #endif  // CHROME_BROWSER_CHROMEOS_MEMORY_OOM_PRIORITY_MANAGER_H_