Add ContentSettingsProvider Interface.

chrome/browser/content_settings/host_content_settings_map.h

Index: chrome/browser/content_settings/host_content_settings_map.h
diff --git a/chrome/browser/content_settings/host_content_settings_map.h b/chrome/browser/content_settings/host_content_settings_map.h
index e43309fb8002d5e7f63dd17f2bc7ee9933553318..ec6030047b05ad846c2e713c32f7fc10758fbd9d 100644
--- a/chrome/browser/content_settings/host_content_settings_map.h
+++ b/chrome/browser/content_settings/host_content_settings_map.h
@@ -25,8 +25,11 @@
 #include "chrome/common/notification_observer.h"
 #include "chrome/common/notification_registrar.h"
 
-class ContentSettingsDetails;
+namespace content_settings {
 class DefaultContentSettingsProvider;
+}  // namespace content_settings
+
+class ContentSettingsDetails;
 class DictionaryValue;
 class GURL;
 class PrefService;
@@ -229,7 +232,7 @@ class HostContentSettingsMap
   bool updating_preferences_;
 
   // Content setting providers.
-  std::vector<linked_ptr<DefaultContentSettingsProvider> >
+  std::vector<linked_ptr<content_settings::DefaultContentSettingsProvider> >
       default_content_settings_providers_;
 
   // Used around accesses to the following objects to guarantee thread safety.