Make DefaultComponentInstallerTest's SequencedWorkerPool multi-threaded.

components/component_updater/default_component_installer_unittest.cc

 // Copyright 2016 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 <iterator>
 #include <string>
 #include <utility>
 #include <vector>
 
 #include "base/callback.h"
@@ skipping 114 matching lines @@
   ComponentUpdateService* component_updater() {
     return component_updater_.get();
   }
   scoped_refptr<TestConfigurator> configurator() const { return config_; }
   base::Closure quit_closure() const { return quit_closure_; }
 
  protected:
   void RunThreads();
 
  private:
-  static const int kNumWorkerThreads_ = 1;
+  static const int kNumWorkerThreads_ = 2;
 
   base::MessageLoopForUI message_loop_;
   base::RunLoop runloop_;
   base::Closure quit_closure_;
 
   std::unique_ptr<base::SequencedWorkerPoolOwner> worker_pool_;
 
   scoped_refptr<TestConfigurator> config_;
   scoped_refptr<MockUpdateClient> update_client_;
   std::unique_ptr<ComponentUpdateService> component_updater_;
@@ skipping 80 matching lines @@
       component.pk_hash);
   EXPECT_EQ(base::Version("0.0.0.0"), component.version);
   EXPECT_TRUE(component.fingerprint.empty());
   EXPECT_STREQ("fake name", component.name.c_str());
   EXPECT_EQ(expected_attrs, component.installer_attributes);
   EXPECT_TRUE(component.requires_network_encryption);
   EXPECT_TRUE(component.supports_group_policy_enable_component_updates);
 }
 
 }  // namespace component_updater