Implement sidebar support for extension action popups

extensions/browser/extension_system.h

Index: extensions/browser/extension_system.h
diff --git a/extensions/browser/extension_system.h b/extensions/browser/extension_system.h
index 099a99fdb1a6ba07eff0bc4346e31cda9347869c..8e66b31e0b0b297edbb57a361574ecd9d33bad2f 100644
--- a/extensions/browser/extension_system.h
+++ b/extensions/browser/extension_system.h
@@ -38,6 +38,7 @@ class OneShotEvent;
 class QuotaService;
 class RuntimeData;
 class SharedUserScriptMaster;
+class SidebarManager;
 class StateStore;
 
 // ExtensionSystem manages the lifetime of many of the services used by the
@@ -111,6 +112,8 @@ class ExtensionSystem : public KeyedService {
   // so it can be retrieved from ExtensionSystem directly.
   virtual scoped_ptr<ExtensionSet> GetDependentExtensions(
       const Extension* extension) = 0;
+
+  virtual SidebarManager* sidebar_manager() = 0;
 };
 
 }  // namespace extensions