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

chrome/browser/component_updater/component_updater_service.h

Index: chrome/browser/component_updater/component_updater_service.h
diff --git a/chrome/browser/component_updater/component_updater_service.h b/chrome/browser/component_updater/component_updater_service.h
index ff01c8975574e9eaebf9fd8343ca25b683079444..c94a163e913e0e069076aa1686cd537be1682e9b 100644
--- a/chrome/browser/component_updater/component_updater_service.h
+++ b/chrome/browser/component_updater/component_updater_service.h
@@ -38,7 +38,7 @@ class OnDemandUpdater;
 // given to ComponentUpdateService::RegisterComponent().
 class ComponentInstaller {
  public:
-  // Called by the component updater on the UI thread when there was a
+  // Called by the component updater on the main thread when there was a
   // problem unpacking or verifying the component. |error| is a non-zero
   // value which is only meaningful to the component updater.
   virtual void OnUpdateError(int error) = 0;
@@ -46,7 +46,8 @@ class ComponentInstaller {
   // Called by the component updater when a component has been unpacked
   // and is ready to be installed. |manifest| contains the CRX manifest
   // json dictionary and |unpack_path| contains the temporary directory
-  // with all the unpacked CRX files.
+  // with all the unpacked CRX files. This method may be called from
+  // a thread other than the main thread.
   virtual bool Install(const base::DictionaryValue& manifest,
                        const base::FilePath& unpack_path) = 0;
 
@@ -96,7 +97,7 @@ struct CrxUpdateItem;
 // notifications are fired, like COMPONENT_UPDATER_STARTED and
 // COMPONENT_UPDATE_FOUND. See notification_type.h for more details.
 //
-// All methods are safe to call ONLY from chrome's UI thread.
+// All methods are safe to call ONLY from the browser's main thread.
 class ComponentUpdateService {
  public:
   enum Status { kOk, kReplaced, kInProgress, kError };