[CacheStorage] Give cache directories unique names

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; }
+  message Cache {
+    required string name = 1;
+    optional string cache_dir = 2;
+  }
   repeated Cache cache = 1;
   optional string origin = 2;
 }
 
 message CacheHeaderMap {
   required string name = 1;
   required string value = 2;
 }
 
 message CacheRequest {
@@ skipping 15 matching lines @@
   required string status_text = 2;
   required ResponseType response_type = 3;
   repeated CacheHeaderMap headers = 4;
   optional string url = 5;
 }
 
 message CacheMetadata {
   required CacheRequest request = 1;
   required CacheResponse response = 2;
 }