Keep NaCl plugins used in app background pages alive when active.

ppapi/proxy/plugin_globals.h

Index: ppapi/proxy/plugin_globals.h
diff --git a/ppapi/proxy/plugin_globals.h b/ppapi/proxy/plugin_globals.h
index bc55245d611a10c5dc154529a1749b595ef86134..3587bb86fef18736ec48312c9873b23b91eac3c3 100644
--- a/ppapi/proxy/plugin_globals.h
+++ b/ppapi/proxy/plugin_globals.h
@@ -73,6 +73,7 @@ class PPAPI_PROXY_EXPORT PluginGlobals : public PpapiGlobals {
                                       const std::string& value) OVERRIDE;
   virtual MessageLoopShared* GetCurrentMessageLoop() OVERRIDE;
   base::TaskRunner* GetFileTaskRunner() OVERRIDE;
+  virtual void MarkPluginIsActive() OVERRIDE;
 
   // Returns the channel for sending to the browser.
   IPC::Sender* GetBrowserSender();
@@ -128,6 +129,9 @@ class PPAPI_PROXY_EXPORT PluginGlobals : public PpapiGlobals {
   // The embedder should call this function when the command line is known.
   void set_command_line(const std::string& c) { command_line_ = c; }
 
+  bool plugin_has_been_active() const { return plugin_has_been_active_; }
+  void set_plugin_has_been_active(bool b) { plugin_has_been_active_ = b; }
+
  private:
   class BrowserSender;
 
@@ -160,6 +164,12 @@ class PPAPI_PROXY_EXPORT PluginGlobals : public PpapiGlobals {
   // lazily, since it might not be needed.
   scoped_ptr<base::Thread> file_thread_;
 
+  // Indicates activity by the plugin. Used to monitor when a plugin can be
+  // shutdown due to idleness. Current needs do not require differentiating
+  // between idle state between multiple instances, if any are active they are
+  // all considered active.
+  bool plugin_has_been_active_;
+
   DISALLOW_COPY_AND_ASSIGN(PluginGlobals);
 };