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

services/asset_bundle/main.cc

 // 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.
 
 #include "base/macros.h"
+#include "base/threading/sequenced_worker_pool.h"
 #include "mojo/application/application_runner_chromium.h"
 #include "mojo/public/c/system/main.h"
 #include "mojo/public/cpp/application/application_connection.h"
 #include "mojo/public/cpp/application/application_delegate.h"
 #include "mojo/public/cpp/application/interface_factory.h"
 #include "services/asset_bundle/asset_unpacker_impl.h"
 
 namespace mojo {
 namespace asset_bundle {
 
 class AssetBundleApp : public ApplicationDelegate,
                        public InterfaceFactory<AssetUnpacker> {
  public:
   AssetBundleApp() {}
   ~AssetBundleApp() override {}
 
  private:
   // |ApplicationDelegate| override:
   bool ConfigureIncomingConnection(ApplicationConnection* connection) override {
     connection->AddService<AssetUnpacker>(this);
     return true;
   }
 
   // |InterfaceFactory<AssetUnpacker>| implementation:
   void Create(ApplicationConnection* connection,
               InterfaceRequest<AssetUnpacker> request) override {
-    new AssetUnpackerImpl(request.Pass());
+    // Lazily initialize |sequenced_worker_pool_|. (We can't create it in the
+    // constructor, since AtExitManager is only created in
+    // ApplicationRunnerChromium::Run().)
+    if (!sequenced_worker_pool_) {
+      // TODO(vtl): What's the "right" way to choose the maximum number of
+      // threads?
+      sequenced_worker_pool_ =
+          new base::SequencedWorkerPool(4, "AssetBundleWorker");
+    }
+
+    new AssetUnpackerImpl(
+        request.Pass(),
+        sequenced_worker_pool_->GetTaskRunnerWithShutdownBehavior(
+            base::SequencedWorkerPool::SKIP_ON_SHUTDOWN));
   }
 
+  // We don't really need the "sequenced" part, but we need to be able to shut
+  // down our worker pool.
+  scoped_refptr<base::SequencedWorkerPool> sequenced_worker_pool_;
+
   DISALLOW_COPY_AND_ASSIGN(AssetBundleApp);
 };
 
 }  // namespace asset_bundle
 }  // namespace mojo
 
 MojoResult MojoMain(MojoHandle application_request) {
   mojo::ApplicationRunnerChromium runner(
       new mojo::asset_bundle::AssetBundleApp());
   return runner.Run(application_request);
 }