Use string16 for cache_name in the back end of CacheStorage.

content/browser/cache_storage/cache_storage.proto

 // Copyright 2014 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.
 
 syntax = "proto2";
 
 option optimize_for = LITE_RUNTIME;
 
 package content;
 
 message CacheStorageIndex {
   message Cache {
     required string name = 1;
     optional string cache_dir = 2;
+    // To support UTF-16 properly, we use bytes type. See crbug.com/432746.
+    optional bytes name_utf16 = 3;
   }
   repeated Cache cache = 1;
   optional string origin = 2;
 }
 
 message CacheHeaderMap {
   required string name = 1;
   required string value = 2;
 }
 
@@ skipping 17 matching lines @@
   required ResponseType response_type = 3;
   repeated CacheHeaderMap headers = 4;
   optional string url = 5;
   optional int64 response_time = 6;
 }
 
 message CacheMetadata {
   required CacheRequest request = 1;
   required CacheResponse response = 2;
 }