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

chrome/browser/component_updater/widevine_cdm_component_installer.cc

Index: chrome/browser/component_updater/widevine_cdm_component_installer.cc
diff --git a/chrome/browser/component_updater/widevine_cdm_component_installer.cc b/chrome/browser/component_updater/widevine_cdm_component_installer.cc
index b3438f5873aef978d0ef9441745587b008ca0afd..5e5877dc83b27451e677da7422791dac9d450a21 100644
--- a/chrome/browser/component_updater/widevine_cdm_component_installer.cc
+++ b/chrome/browser/component_updater/widevine_cdm_component_installer.cc
@@ -20,6 +20,7 @@
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_split.h"
 #include "base/strings/utf_string_conversions.h"
+#include "base/threading/sequenced_worker_pool.h"
 #include "base/values.h"
 #include "build/build_config.h"
 #include "chrome/browser/component_updater/component_updater_service.h"
@@ -363,8 +364,12 @@ void RegisterWidevineCdmComponent(ComponentUpdateService* cus) {
   scoped_ptr<ComponentInstallerTraits> traits(
       new WidevineCdmComponentInstallerTraits);
   // |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(),
+              base::SequencedWorkerPool::SKIP_ON_SHUTDOWN));
   installer->Register(cus);
 #else
   return;