Add KeepaliveImpulse to extension process manager.

extensions/browser/process_manager.h

 // Copyright 2013 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 EXTENSIONS_BROWSER_PROCESS_MANAGER_H_
 #define EXTENSIONS_BROWSER_PROCESS_MANAGER_H_
 
 #include <map>
 #include <set>
 #include <string>
@@ skipping 68 matching lines @@
 
   // Returns true if the (lazy) background host for the given extension has
   // already been sent the unload event and is shutting down.
   bool IsBackgroundHostClosing(const std::string& extension_id);
 
   // Getter and setter for the lazy background page's keepalive count. This is
   // the count of how many outstanding "things" are keeping the page alive.
   // When this reaches 0, we will begin the process of shutting down the page.
   // "Things" include pending events, resource loads, and API calls.
   int GetLazyKeepaliveCount(const Extension* extension);
-  int IncrementLazyKeepaliveCount(const Extension* extension);
-  int DecrementLazyKeepaliveCount(const Extension* extension);
+  void IncrementLazyKeepaliveCount(const Extension* extension);
+  void DecrementLazyKeepaliveCount(const Extension* extension);
 
   void IncrementLazyKeepaliveCountForView(
       content::RenderViewHost* render_view_host);
 
+  // Keeps a background page alive. Unlike IncrementLazyKeepaliveCount, these
+  // impulses will only keep the page alive for a limited amount of time unless
+  // called regularly.
+  void KeepaliveImpulse(const Extension* extension);
+
   // Handles a response to the ShouldSuspend message, used for lazy background
   // pages.
   void OnShouldSuspendAck(const std::string& extension_id, int sequence_id);
 
   // Same as above, for the Suspend message.
   void OnSuspendAck(const std::string& extension_id);
 
   // Tracks network requests for a given RenderViewHost, used to know
   // when network activity is idle for lazy background pages.
   void OnNetworkRequestStarted(content::RenderViewHost* render_view_host);
@@ skipping 52 matching lines @@
   typedef std::map<ExtensionId, BackgroundPageData> BackgroundPageDataMap;
   typedef std::map<content::RenderViewHost*,
       extensions::ViewType> ExtensionRenderViews;
 
   // Called just after |host| is created so it can be registered in our lists.
   void OnBackgroundHostCreated(ExtensionHost* host);
 
   // Close the given |host| iff it's a background page.
   void CloseBackgroundHost(ExtensionHost* host);
 
+  // Internal implementation of DecrementLazyKeepaliveCount with an
+  // |extension_id| known to have a lazy background page.
+  void DecrementLazyKeepaliveCount(const std::string& extension_id);
+
+  // Checks if keepalive impulses have occured, and adjusts keep alive count.
+  void OnKeepaliveImpulseCheck();
+
   // These are called when the extension transitions between idle and active.
   // They control the process of closing the background page when idle.
   void OnLazyBackgroundPageIdle(const std::string& extension_id,
                                 int sequence_id);
   void OnLazyBackgroundPageActive(const std::string& extension_id);
   void CloseLazyBackgroundPageNow(const std::string& extension_id,
                                   int sequence_id);
 
   // Potentially registers a RenderViewHost, if it is associated with an
   // extension. Does nothing if this is not an extension renderer.
@@ skipping 35 matching lines @@
   base::Callback<void(content::DevToolsAgentHost*, bool)> devtools_callback_;
 
   base::WeakPtrFactory<ProcessManager> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ProcessManager);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_BROWSER_PROCESS_MANAGER_H_