Use WebIDBKeyPath type in WebKit API, implement IndexedDBKeyPath type.

content/common/indexed_db/indexed_db_messages.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Message definition file, included multiple times, hence no include guard.
 
 #include <vector>
 
 #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_key_range.h"
 #include "content/common/indexed_db/indexed_db_param_traits.h"
 #include "content/public/common/serialized_script_value.h"
 #include "ipc/ipc_message_macros.h"
 #include "ipc/ipc_param_traits.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebExceptionCode.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebIDBObjectStore.h"
 
 #define IPC_MESSAGE_START IndexedDBMsgStart
 
@@ skipping 30 matching lines @@
   IPC_STRUCT_MEMBER(string16, origin)
   // The name of the database.
   IPC_STRUCT_MEMBER(string16, name)
 IPC_STRUCT_END()
 
 // Used to create an object store.
 IPC_STRUCT_BEGIN(IndexedDBHostMsg_DatabaseCreateObjectStore_Params)
   // The name of the object store.
   IPC_STRUCT_MEMBER(string16, name)
   // The keyPath of the object store.
-  IPC_STRUCT_MEMBER(NullableString16, key_path)
+  IPC_STRUCT_MEMBER(IndexedDBKeyPath, key_path)
   // Whether the object store created should have a key generator.
   IPC_STRUCT_MEMBER(bool, auto_increment)
   // The transaction this is associated with.
   IPC_STRUCT_MEMBER(int32, transaction_id)
   // The database the object store belongs to.
   IPC_STRUCT_MEMBER(int32, idb_database_id)
 IPC_STRUCT_END()
 
 // Used to open both cursors and object cursors in IndexedDB.
 IPC_STRUCT_BEGIN(IndexedDBHostMsg_IndexOpenCursor_Params)
@@ skipping 50 matching lines @@
   IPC_STRUCT_MEMBER(WebKit::WebIDBObjectStore::PutMode, put_mode)
   // The transaction it's associated with.
   IPC_STRUCT_MEMBER(int, transaction_id)
 IPC_STRUCT_END()
 
 // Used to create an index.
 IPC_STRUCT_BEGIN(IndexedDBHostMsg_ObjectStoreCreateIndex_Params)
   // The name of the index.
   IPC_STRUCT_MEMBER(string16, name)
   // The keyPath of the index.
-  IPC_STRUCT_MEMBER(NullableString16, key_path)
+  IPC_STRUCT_MEMBER(IndexedDBKeyPath, key_path)
   // Whether the index created has unique keys.
   IPC_STRUCT_MEMBER(bool, unique)
   // Whether the index created produces keys for each array entry.
   IPC_STRUCT_MEMBER(bool, multi_entry)
   // The transaction this is associated with.
   IPC_STRUCT_MEMBER(int32, transaction_id)
   // The object store the index belongs to.
   IPC_STRUCT_MEMBER(int32, idb_object_store_id)
 IPC_STRUCT_END()
 
@@ skipping 259 matching lines @@
                             string16 /* name */)
 
 // WebIDBIndex::storeName() message.
 IPC_SYNC_MESSAGE_CONTROL1_1(IndexedDBHostMsg_IndexStoreName,
                             int32, /* idb_index_id */
                             string16 /* store_name */)
 
 // WebIDBIndex::keyPath() message.
 IPC_SYNC_MESSAGE_CONTROL1_1(IndexedDBHostMsg_IndexKeyPath,
                             int32, /* idb_index_id */
-                            NullableString16 /* key_path */)
+                            IndexedDBKeyPath /* key_path */)
 
 // WebIDBIndex::unique() message.
 IPC_SYNC_MESSAGE_CONTROL1_1(IndexedDBHostMsg_IndexUnique,
                             int32, /* idb_index_id */
                             bool /* unique */)
 
 // WebIDBIndex::multiEntry() message.
 IPC_SYNC_MESSAGE_CONTROL1_1(IndexedDBHostMsg_IndexMultiEntry,
                             int32, /* idb_index_id */
                             bool /* multi_entry */)
@@ skipping 36 matching lines @@
                      int32 /* idb_index_id */)
 
 // WebIDBObjectStore::name() message.
 IPC_SYNC_MESSAGE_CONTROL1_1(IndexedDBHostMsg_ObjectStoreName,
                             int32, /* idb_object_store_id */
                             string16 /* name */)
 
 // WebIDBObjectStore::keyPath() message.
 IPC_SYNC_MESSAGE_CONTROL1_1(IndexedDBHostMsg_ObjectStoreKeyPath,
                             int32, /* idb_object_store_id */
-                            NullableString16 /* keyPath */)
+                            IndexedDBKeyPath /* keyPath */)
 
 // WebIDBObjectStore::indexNames() message.
 IPC_SYNC_MESSAGE_CONTROL1_1(IndexedDBHostMsg_ObjectStoreIndexNames,
                             int32, /* idb_object_store_id */
                             std::vector<string16> /* index_names */)
 
 // WebIDBObjectStore::get() message.
 IPC_SYNC_MESSAGE_CONTROL5_1(IndexedDBHostMsg_ObjectStoreGet,
                             int32, /* idb_object_store_id */
                             int32, /* thread_id */
@@ skipping 87 matching lines @@
 IPC_MESSAGE_CONTROL1(IndexedDBHostMsg_TransactionAbort,
                      int32 /* idb_transaction_id */)
 
 // IDBTransaction::DidCompleteTaskEvents() message.
 IPC_MESSAGE_CONTROL1(IndexedDBHostMsg_TransactionDidCompleteTaskEvents,
                      int32 /* idb_transaction_id */)
 
 // WebIDBTransaction::~WebIDBTransaction() message.
 IPC_MESSAGE_CONTROL1(IndexedDBHostMsg_TransactionDestroyed,
                      int32 /* idb_transaction_id */)