Add an arbitrary delay before unloading lazy background pages.

chrome/browser/extensions/extension_process_manager.h

Index: chrome/browser/extensions/extension_process_manager.h
diff --git a/chrome/browser/extensions/extension_process_manager.h b/chrome/browser/extensions/extension_process_manager.h
index 9e9df0803813a0930e64a16f353bb23fa366ff48..03c58ec87c002f288f805e642662d3184d692dcc 100644
--- a/chrome/browser/extensions/extension_process_manager.h
+++ b/chrome/browser/extensions/extension_process_manager.h
@@ -12,6 +12,7 @@
 
 #include "base/compiler_specific.h"
 #include "base/memory/ref_counted.h"
+#include "base/memory/weak_ptr.h"
 #include "content/public/common/view_type.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
@@ -182,7 +183,8 @@ class ExtensionProcessManager : public content::NotificationObserver {
 
   // 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);
+  void OnLazyBackgroundPageIdle(const std::string& extension_id,
+                                int close_sequence_id);
   void OnLazyBackgroundPageActive(const std::string& extension_id);
 
   // Updates a potentially-registered RenderViewHost once it has been
@@ -192,6 +194,8 @@ class ExtensionProcessManager : public content::NotificationObserver {
 
   BackgroundPageDataMap background_page_data_;
 
+  base::WeakPtrFactory<ExtensionProcessManager> weak_ptr_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(ExtensionProcessManager);
 };