[fsp] Let extensions decide about the file system id.

chrome/browser/chromeos/file_system_provider/operations/operation.cc

 // 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.
 
 #include "chrome/browser/chromeos/file_system_provider/operations/operation.h"
 
 #include "chrome/browser/chromeos/file_system_provider/provided_file_system_info.h"
 #include "extensions/browser/event_router.h"
 
 namespace chromeos {
@@ skipping 27 matching lines @@
 }
 
 void Operation::SetDispatchEventImplForTesting(
     const DispatchEventImplCallback& callback) {
   dispatch_event_impl_ = callback;
 }
 
 bool Operation::SendEvent(int request_id,
                           const std::string& event_name,
                           scoped_ptr<base::ListValue> event_args) {
-  event_args->Insert(
-      0, new base::FundamentalValue(file_system_info_.file_system_id()));
+  event_args->Insert(0,
+                     new base::StringValue(file_system_info_.file_system_id()));
   event_args->Insert(1, new base::FundamentalValue(request_id));
 
   return dispatch_event_impl_.Run(
       make_scoped_ptr(new extensions::Event(event_name, event_args.Pass())));
 }
 
 }  // namespace operations
 }  // namespace file_system_provider
 }  // namespace chromeos