Componentize component_updater: Replace content::BrowserThread usage with task runners

chrome/browser/component_updater/cld_component_installer.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/component_updater/cld_component_installer.h"
 
 #include <string>
 #include <vector>
 
 #include "base/bind.h"
 #include "base/file_util.h"
 #include "base/files/file_path.h"
 #include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/path_service.h"
-#include "chrome/browser/profiles/profile.h"
+#include "base/threading/sequenced_worker_pool.h"
 #include "components/component_updater/component_updater_paths.h"
 #include "components/translate/content/browser/data_file_browser_cld_data_provider.h"
 #include "content/public/browser/browser_thread.h"
 #include "net/ssl/ssl_config_service.h"
 
 using component_updater::ComponentUpdateService;
-using content::BrowserThread;
 
 namespace {
 // TODO(andrewhayden): Make the data file path into a gyp/gn define
 // If you change this, also update component_cld_data_harness.cc
 // and cld_component_installer_unittest.cc accordingly!
 const base::FilePath::CharType kCldDataFileName[] =
     FILE_PATH_LITERAL("cld2_data.bin");
 }  // namespace
 
 namespace component_updater {
@@ skipping 65 matching lines @@
 }
 
 std::string CldComponentInstallerTraits::GetName() const {
   return kCldManifestName;
 }
 
 void RegisterCldComponent(ComponentUpdateService* cus) {
   scoped_ptr<ComponentInstallerTraits> traits(
       new CldComponentInstallerTraits());
   // |cus| will take ownership of |installer| during installer->Register(cus).
-  DefaultComponentInstaller* installer =
-      new DefaultComponentInstaller(traits.Pass());
+  DefaultComponentInstaller* installer = new DefaultComponentInstaller(
+      traits.Pass(),
+      content::BrowserThread::GetBlockingPool()
+          ->GetSequencedTaskRunnerWithShutdownBehavior(
+              content::BrowserThread::GetBlockingPool()->GetSequenceToken(),

[blundell, 2014/07/15 08:45:20]

What logic is behind the choices on lines 112 and 113 (and elsewhere throughout
this CL)?

[tommycli, 2014/07/15 18:58:25]

I replicated the choices made here: 

https://code.google.com/p/chromium/codesearch#chromium/src/chrome/browser/com...

In another version of this patch, which I didn't upload, I used:
  ComponentUpdateService::GetConfig()->GetSequencedTaskRunner(), but this
requires adding a GetConfig method to ComponentUpdateService.

Do you prefer that?

+              base::SequencedWorkerPool::SKIP_ON_SHUTDOWN));
   installer->Register(cus);
 }
 
 void CldComponentInstallerTraits::SetLatestCldDataFile(
     const base::FilePath& path) {
   VLOG(1) << "Setting CLD data file location: " << path.value();
   translate::DataFileBrowserCldDataProvider::SetCldDataFilePath(path);
 }
 
 }  // namespace component_updater