Move Extension into extensions namespace

chrome/browser/themes/theme_service_factory.h

Index: chrome/browser/themes/theme_service_factory.h
diff --git a/chrome/browser/themes/theme_service_factory.h b/chrome/browser/themes/theme_service_factory.h
index 9b590b1d969c99468b1b58805a7977720ea7134b..2b688ec691871e71d441727ec8ee21b26e3c6481 100644
--- a/chrome/browser/themes/theme_service_factory.h
+++ b/chrome/browser/themes/theme_service_factory.h
@@ -9,9 +9,12 @@
 #include "base/memory/singleton.h"
 #include "chrome/browser/profiles/profile_keyed_service_factory.h"
 
+class Profile;
 class ThemeService;
+
+namespace extensions {
 class Extension;
-class Profile;
+}
 
 // Singleton that owns all ThemeServices and associates them with
 // Profiles. Listens for the Profile's destruction notification and cleans up
@@ -26,7 +29,7 @@ class ThemeServiceFactory : public ProfileKeyedServiceFactory {
   // Returns the Extension that implements the theme associated with
   // |profile|. Returns NULL if the theme is no longer installed, if there is
   // no installed theme, or the theme was cleared.
-  static const Extension* GetThemeForProfile(Profile* profile);
+  static const extensions::Extension* GetThemeForProfile(Profile* profile);
 
   static ThemeServiceFactory* GetInstance();