Don't use base::WorkerPool in the asset_bundle app.

services/asset_bundle/asset_bundle_impl.h

 // Copyright 2015 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.
 
 #ifndef SERVICES_ASSET_BUNDLE_ASSET_BUNDLE_IMPL_H_
 #define SERVICES_ASSET_BUNDLE_ASSET_BUNDLE_IMPL_H_
 
 #include "base/files/scoped_temp_dir.h"
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/task_runner.h"
 #include "mojo/public/cpp/bindings/interface_request.h"
 #include "mojo/public/cpp/bindings/strong_binding.h"
 #include "mojo/public/cpp/system/data_pipe.h"
 #include "mojo/services/asset_bundle/public/interfaces/asset_bundle.mojom.h"
 
 namespace mojo {
 namespace asset_bundle {
 
 class AssetBundleImpl : public AssetBundle {
  public:
   AssetBundleImpl(InterfaceRequest<AssetBundle> request,
-                  scoped_ptr<base::ScopedTempDir> asset_dir);
+                  scoped_ptr<base::ScopedTempDir> asset_dir,
+                  scoped_refptr<base::TaskRunner> worker_runner);
   ~AssetBundleImpl() override;
 
   // AssetBundle implementation
   void GetAsStream(
       const String& asset_name,
       const Callback<void(ScopedDataPipeConsumerHandle)>& callback) override;
 
  private:
   StrongBinding<AssetBundle> binding_;
   scoped_ptr<base::ScopedTempDir> asset_dir_;
+  scoped_refptr<base::TaskRunner> worker_runner_;
 
   DISALLOW_COPY_AND_ASSIGN(AssetBundleImpl);
 };
 
 }  // namespace asset_bundle
 }  // namespace mojo
 
 #endif  // SERVICES_ASSET_BUNDLE_ASSET_BUNDLE_IMPL_H_