Make TabLoader a client of memory coordinator

chrome/browser/sessions/tab_loader.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_SESSIONS_TAB_LOADER_H_
 #define CHROME_BROWSER_SESSIONS_TAB_LOADER_H_
 
 #include <stddef.h>
 
 #include <list>
 #include <memory>
 #include <set>
 
 #include "base/macros.h"
+#include "base/memory/memory_coordinator_client.h"
 #include "base/memory/memory_pressure_listener.h"
 #include "base/timer/timer.h"
 #include "chrome/browser/sessions/session_restore_delegate.h"
 #include "chrome/browser/sessions/tab_loader_delegate.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 
 namespace content {
 class NavigationController;
 class RenderWidgetHost;
 }
 
 class SessionRestoreStatsCollector;
 
 // TabLoader is responsible for loading tabs after session restore has finished
 // creating all the tabs. Tabs are loaded after a previously tab finishes
 // loading or a timeout is reached. If the timeout is reached before a tab
 // finishes loading the timeout delay is doubled.
 //
 // TabLoader keeps a reference to itself when it's loading. When it has finished
 // loading, it drops the reference. If another profile is restored while the
 // TabLoader is loading, it will schedule its tabs to get loaded by the same
 // TabLoader. When doing the scheduling, it holds a reference to the TabLoader.
 //
 // This is not part of SessionRestoreImpl so that synchronous destruction
 // of SessionRestoreImpl doesn't have timing problems.
 class TabLoader : public content::NotificationObserver,
                   public base::RefCounted<TabLoader>,
-                  public TabLoaderCallback {
+                  public TabLoaderCallback,
+                  public base::MemoryCoordinatorClient {
  public:
   using RestoredTab = SessionRestoreDelegate::RestoredTab;
 
   // NotificationObserver method. Removes the specified tab and loads the next
   // tab.
   void Observe(int type,
                const content::NotificationSource& source,
                const content::NotificationDetails& details) override;
 
   // TabLoaderCallback:
@@ skipping 42 matching lines @@
   // NULL otherwise.
   static content::RenderWidgetHost* GetRenderWidgetHost(
       content::NavigationController* controller);
 
   // Register for necessary notifications on a tab navigation controller.
   void RegisterForNotifications(content::NavigationController* controller);
 
   // Called when a tab goes away or a load completes.
   void HandleTabClosedOrLoaded(content::NavigationController* controller);
 
-  // Convenience function returning the current memory pressure level.
-  base::MemoryPressureListener::MemoryPressureLevel
-      CurrentMemoryPressureLevel();
+  // Returns true when this is under memory pressure and required to purge
+  // memory by stopping loading tabs.
+  bool ShouldStopLoadingTabs() const;
 
   // React to memory pressure by stopping to load any more tabs.
   void OnMemoryPressure(
       base::MemoryPressureListener::MemoryPressureLevel memory_pressure_level);
 
+  // base::MemoryCoordinatorClient implementation:
+  void OnMemoryStateChange(base::MemoryState state) override;
+
+  // Stops loading tabs to purge memory by stopping to load any more tabs.
+  void StopLoadingTabs();
+
   std::unique_ptr<TabLoaderDelegate> delegate_;
 
   // Listens for system under memory pressure notifications and stops loading
   // of tabs when we start running out of memory.
   base::MemoryPressureListener memory_pressure_listener_;
 
+  // TODO(hajimehoshi): Remove this after implementing new API to get its
+  // current state instead.
+  base::MemoryState memory_state_;

[haraken, 2016/10/11 08:36:23]

Is it hard to implement the API to get MemoryState?

It's unfortunate that you're adding memory_state_ to a bunch of places. If it's
easy to implement the API, it's better to land the API first.

[sky, 2016/10/11 17:47:42]

+1

[hajimehoshi, 2016/10/24 10:16:57]

Done.

+
   content::NotificationRegistrar registrar_;
 
   // The delay timer multiplier. See class description for details.
   size_t force_load_delay_multiplier_;
 
   // True if the tab loading is enabled.
   bool loading_enabled_;
 
   // The set of tabs we've initiated loading on. This does NOT include the
   // selected tabs.
@@ skipping 15 matching lines @@
   // explicitly referenced so that it can be notified of deferred tab loads due
   // to memory pressure.
   scoped_refptr<SessionRestoreStatsCollector> stats_collector_;
 
   static TabLoader* shared_tab_loader_;
 
   DISALLOW_COPY_AND_ASSIGN(TabLoader);
 };
 
 #endif  // CHROME_BROWSER_SESSIONS_TAB_LOADER_H_