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

ppapi/shared_impl/ppapi_globals.h

Index: ppapi/shared_impl/ppapi_globals.h
diff --git a/ppapi/shared_impl/ppapi_globals.h b/ppapi/shared_impl/ppapi_globals.h
index 93ab2998e3476d04b6e0c372adb155c058cc56b8..d9be03877e4aa6f6ceaab67469ffb7ee59a41656 100644
--- a/ppapi/shared_impl/ppapi_globals.h
+++ b/ppapi/shared_impl/ppapi_globals.h
@@ -128,6 +128,12 @@ class PPAPI_SHARED_EXPORT PpapiGlobals {
   virtual bool IsHostGlobals() const;
   virtual bool IsPluginGlobals() const;
 
+  // Records that the plugin is active. The plugin reports that it is active to
+  // containers that monitor and shutdown idle content such as background apps.
+  // This method only has an effect on the plugin process, calls from the
+  // renderer process will have no effect.
+  virtual void MarkPluginIsActive();
+
  private:
   // Return the thread-local pointer which is used only for unit testing. It
   // should always be NULL when running in production. It allows separate