Use WebIDBKeyPath type in WebKit API, implement IndexedDBKeyPath type.

content/utility/utility_thread_impl.h

Index: content/utility/utility_thread_impl.h
diff --git a/content/utility/utility_thread_impl.h b/content/utility/utility_thread_impl.h
index b0c20a2c45139e5a6fe7a2f78a5b5019cc4dc566..32b7a8c8a8f6d1102f4d6666d59a4122cad947a4 100644
--- a/content/utility/utility_thread_impl.h
+++ b/content/utility/utility_thread_impl.h
@@ -11,13 +11,13 @@
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
-#include "base/string16.h"
 #include "content/common/child_thread.h"
 #include "content/common/content_export.h"
 #include "content/public/utility/utility_thread.h"
 
 class FilePath;
 class IndexedDBKey;
+class IndexedDBKeyPath;
 
 namespace content {
 class SerializedScriptValue;
@@ -47,10 +47,10 @@ class UtilityThreadImpl : public content::UtilityThread,
       int id,
       const std::vector<content::SerializedScriptValue>&
           serialized_script_values,
-      const string16& idb_key_path);
+      const IndexedDBKeyPath& idb_key_path);
   void OnInjectIDBKey(const IndexedDBKey& key,
                       const content::SerializedScriptValue& value,
-                      const string16& key_path);
+                      const IndexedDBKeyPath& key_path);
   void OnBatchModeStarted();
   void OnBatchModeFinished();