Move nullable_string16.h to the string subdirectory.

webkit/browser/dom_storage/dom_storage_host.h

Index: webkit/browser/dom_storage/dom_storage_host.h
diff --git a/webkit/browser/dom_storage/dom_storage_host.h b/webkit/browser/dom_storage/dom_storage_host.h
index 7dd1eabcbc8e0f28f3716e649b5ea6a30e79a37e..f15a3f1f5dc5ef6089fca8fe87b854af9c448500 100644
--- a/webkit/browser/dom_storage/dom_storage_host.h
+++ b/webkit/browser/dom_storage/dom_storage_host.h
@@ -8,7 +8,7 @@
 #include <map>
 
 #include "base/memory/ref_counted.h"
-#include "base/nullable_string16.h"
+#include "base/strings/nullable_string16.h"
 #include "base/strings/string16.h"
 #include "webkit/common/dom_storage/dom_storage_types.h"
 #include "webkit/storage/webkit_storage_export.h"
@@ -37,11 +37,12 @@ class WEBKIT_STORAGE_EXPORT DomStorageHost {
   void CloseStorageArea(int connection_id);
   bool ExtractAreaValues(int connection_id, ValuesMap* map);
   unsigned GetAreaLength(int connection_id);
-  NullableString16 GetAreaKey(int connection_id, unsigned index);
-  NullableString16 GetAreaItem(int connection_id, const base::string16& key);
+  base::NullableString16 GetAreaKey(int connection_id, unsigned index);
+  base::NullableString16 GetAreaItem(int connection_id,
+                                     const base::string16& key);
   bool SetAreaItem(int connection_id, const base::string16& key,
                    const base::string16& value, const GURL& page_url,
-                   NullableString16* old_value);
+                   base::NullableString16* old_value);
   bool RemoveAreaItem(int connection_id, const base::string16& key,
                   const GURL& page_url,
                   base::string16* old_value);