Use WebIDBKeyPath type in WebKit API, implement IndexedDBKeyPath type.

content/common/indexed_db/indexed_db_param_traits.h

Index: content/common/indexed_db/indexed_db_param_traits.h
diff --git a/content/common/indexed_db/indexed_db_param_traits.h b/content/common/indexed_db/indexed_db_param_traits.h
index 3dfd5b84857dab564b68cf59fbb67bd16c48d5d9..170cd2e222b0f208470fd454b7539dbee86b5aac 100644
--- a/content/common/indexed_db/indexed_db_param_traits.h
+++ b/content/common/indexed_db/indexed_db_param_traits.h
@@ -10,6 +10,7 @@
 #include "ipc/ipc_param_traits.h"
 
 class IndexedDBKey;
+class IndexedDBKeyPath;
 class IndexedDBKeyRange;
 
 namespace content {
@@ -40,6 +41,14 @@ struct ParamTraits<IndexedDBKey> {
 };
 
 template <>
+struct ParamTraits<IndexedDBKeyPath> {
+  typedef IndexedDBKeyPath param_type;
+  static void Write(Message* m, const param_type& p);
+  static bool Read(const Message* m, PickleIterator* iter, param_type* r);
+  static void Log(const param_type& p, std::string* l);
+};
+
+template <>
 struct ParamTraits<IndexedDBKeyRange> {
   typedef IndexedDBKeyRange param_type;
   static void Write(Message* m, const param_type& p);