Use WebIDBKeyPath type in WebKit API, implement IndexedDBKeyPath type.

content/common/utility_messages.h

Index: content/common/utility_messages.h
diff --git a/content/common/utility_messages.h b/content/common/utility_messages.h
index c336352ee371a1a4351a9a48e6cf9af28f08255e..2087ca223f12b7744ec92db8ed85e8b3d6d26af3 100644
--- a/content/common/utility_messages.h
+++ b/content/common/utility_messages.h
@@ -10,6 +10,7 @@
 #include "base/basictypes.h"
 #include "content/common/content_export.h"
 #include "content/common/indexed_db/indexed_db_key.h"
+#include "content/common/indexed_db/indexed_db_key_path.h"
 #include "content/common/indexed_db/indexed_db_param_traits.h"
 #include "content/public/common/common_param_traits.h"
 #include "content/public/common/serialized_script_value.h"
@@ -29,12 +30,12 @@
 IPC_MESSAGE_CONTROL3(UtilityMsg_IDBKeysFromValuesAndKeyPath,
                      int,     // id
                      std::vector<content::SerializedScriptValue>,
-                     string16)  // IDBKeyPath
+                     IndexedDBKeyPath)
 
 IPC_MESSAGE_CONTROL3(UtilityMsg_InjectIDBKey,
                      IndexedDBKey /* key */,
                      content::SerializedScriptValue /* value */,
-                     string16 /* key path*/)
+                     IndexedDBKeyPath)
 
 // Tells the utility process that it's running in batch mode.
 IPC_MESSAGE_CONTROL0(UtilityMsg_BatchMode_Started)