Fix crash of ExtensionManagement in guest mode

chrome/browser/extensions/extension_management.h

Index: chrome/browser/extensions/extension_management.h
diff --git a/chrome/browser/extensions/extension_management.h b/chrome/browser/extensions/extension_management.h
index 3f1a40511573c7087f105f822d6a845c6aadd7f1..c9aa11e3dfbde06b15b648d0ad09bad55cfbe5fa 100644
--- a/chrome/browser/extensions/extension_management.h
+++ b/chrome/browser/extensions/extension_management.h
@@ -180,6 +180,8 @@ class ExtensionManagementFactory : public BrowserContextKeyedServiceFactory {
   // BrowserContextKeyedServiceExtensionManagementFactory:
   virtual KeyedService* BuildServiceInstanceFor(
       content::BrowserContext* context) const OVERRIDE;
+  virtual content::BrowserContext* GetBrowserContextToUse(
+      content::BrowserContext* context) const OVERRIDE;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionManagementFactory);
 };