Removed the ProcessHandle from the RendererClosedDetails payload

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"
@@ skipping 61 matching lines @@
     TabStats();
     ~TabStats();
     bool is_app;  // browser window is an app
     bool is_reloadable_ui;  // Reloadable web UI page, like NTP or Settings.
     bool is_playing_audio;
     bool is_pinned;
     bool is_selected;  // selected in the currently active browser window
     bool is_discarded;
     base::TimeTicks last_active;
     base::ProcessHandle renderer_handle;
+    int child_process_id;

[James Cook, 2014/11/20 16:50:35]

I'm confused. This code only runs on Posix, where process_handle.h says that
base::ProcessHandle and base::ProcessId are the same thing. Is this
|child_process_id| referring to a different process than the one from
|renderer_handle|? Do you need both of these?

Or is |child_process_id| not a pid?  If that's the case then the name is
super-confusing.  Perhaps it should be something like child_host_id or
child_process_host_id.

[Charlie Reis, 2014/11/20 17:07:45]

Note: It's pretty common in the browser process to refer to the
RenderProcessHost ID as "process_id," for better or worse.  That said, in cases
like this where it's used alongside the ProcessHandle, it would be less
ambiguous to call it child_process_host_id.

[sramajay, 2014/11/21 12:18:47]

child_process_id is not a pid, it is just a unique auto generated number given
to all child processes including plugin process. 
Yes. It makes sense to rename it as child_process_host_id.

     base::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.
@@ skipping 12 matching lines @@
   void PurgeBrowserMemory();
 
   // Returns the number of tabs open in all browser instances.
   int GetTabCount() const;
 
   TabStatsList GetTabStatsOnUIThread();
 
   // Called when the timer fires, sets oom_adjust_score for all renderers.
   void AdjustOomPriorities();
 
-  // Returns a list of unique process handles from |stats_list|. If multiple
-  // tabs use the same process, returns the first process handle. This implies
-  // that the processes are selected based on their "most important" tab.
-  static std::vector<base::ProcessHandle> GetProcessHandles(
-      const TabStatsList& stats_list);
+  // Returns a list of child process ids from |stats_list| which unique pids.

[James Cook, 2014/11/20 16:50:35]

which -> with? which are?

[sramajay, 2014/11/21 12:18:47]

Done.

+  // If multiple tabs use the same process, returns the first child process id.
+  // This implies that the processes are selected based on their
+  // "most important" tab.
+  static std::vector<int> GetChildProcessIds(const TabStatsList& stats_list);
 
   // Called by AdjustOomPriorities.
   void AdjustOomPrioritiesOnFileThread(TabStatsList stats_list);
 
   // Posts AdjustFocusedTabScore task to the file thread.
   void OnFocusTabScoreAdjustmentTimeout();
 
   // Sets the score of the focused tab to the least value.
   void AdjustFocusedTabScoreOnFileThread();
 
   static bool CompareTabStats(TabStats first, TabStats second);
 
   virtual void Observe(int type,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) override;
 
   base::RepeatingTimer<OomPriorityManager> timer_;
   base::OneShotTimer<OomPriorityManager> focus_tab_score_adjust_timer_;
   base::RepeatingTimer<OomPriorityManager> recent_tab_discard_timer_;
   content::NotificationRegistrar registrar_;
 
   // This lock is for pid_to_oom_score_ and focus_tab_pid_.

[James Cook, 2014/11/20 16:50:35]

Fix this comment, or comment on the individual member variables which lock
protects them.

[sramajay, 2014/11/21 12:18:47]

Done.

-  base::Lock pid_to_oom_score_lock_;
-  // map maintaining the process - oom_score mapping.
-  typedef base::hash_map<base::ProcessHandle, int> ProcessScoreMap;
-  ProcessScoreMap pid_to_oom_score_;
-  base::ProcessHandle focused_tab_pid_;
+  base::Lock oom_score_lock_;
+  // map maintaining the child process id - oom_score mapping.
+  typedef base::hash_map<int, int> ProcessScoreMap;
+  ProcessScoreMap oom_score_map_;
+  base::ProcessHandle focused_tab_process_id_;
 
   // Observer for the kernel low memory signal.  NULL if tab discarding is
   // disabled.
   scoped_ptr<LowMemoryObserver> low_memory_observer_;
 
   // Wall-clock time when the priority manager started running.
   base::TimeTicks start_time_;
 
   // Wall-clock time of last tab discard during this browsing session, or 0 if
   // no discard has happened yet.
   base::TimeTicks last_discard_time_;
 
   // Wall-clock time of last priority adjustment, used to correct the above
   // times for discontinuities caused by suspend/resume.
   base::TimeTicks last_adjust_time_;
 
   // Number of times we have discarded a tab, for statistics.
   int discard_count_;
 
   // Whether a tab discard event has occurred during the last time interval,
   // used for statistics normalized by usage.
   bool recent_tab_discard_;
 
   DISALLOW_COPY_AND_ASSIGN(OomPriorityManager);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_MEMORY_OOM_PRIORITY_MANAGER_H_