diff --git a/chrome/browser/component_updater/background_downloader_win.cc b/chrome/browser/component_updater/background_downloader_win.cc
index 004f5f28..dff644e 100644
--- a/chrome/browser/component_updater/background_downloader_win.cc
+++ b/chrome/browser/component_updater/background_downloader_win.cc
@@ -396,6 +396,19 @@
 }
 
 BackgroundDownloader::~BackgroundDownloader() {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+
+  // The following objects have thread affinity and can't be destroyed on the
+  // UI thread. The resources managed by these objects are acquired at the
+  // beginning of a download and released at the end of the download. Most of
+  // the time, when this destructor is called, these resources have been already
+  // disposed by. Releasing the ownership here is a NOP. However, if the browser
+  // is shutting down while a download is in progress, the timer is active and
+  // the interface pointers are valid. Releasing the ownership means leaking
+  // these objects and their associated resources.
+  timer_.release();
+  bits_manager_.Detach();
+  job_.Detach();
 }
 
 void BackgroundDownloader::DoStartDownload(const GURL& url) {
diff --git a/chrome/browser/component_updater/background_downloader_win.h b/chrome/browser/component_updater/background_downloader_win.h
index d1a08f84..500bef8 100644
--- a/chrome/browser/component_updater/background_downloader_win.h
+++ b/chrome/browser/component_updater/background_downloader_win.h
@@ -20,7 +20,9 @@
 // Implements a downloader in terms of the BITS service. The public interface
 // of this class and the CrxDownloader overrides are expected to be called
 // from the UI thread. The rest of the class code runs on the FILE thread in
-// a single threaded apartment.
+// a single threaded apartment. Instances of this class are created and
+// destroyed in the UI thread. See the implementation of the class destructor
+// for details regarding the clean up of resources acquired in this class.
 class BackgroundDownloader : public CrxDownloader {
  protected:
   friend class CrxDownloader;
@@ -70,6 +72,9 @@
   net::URLRequestContextGetter* context_getter_;
   scoped_refptr<base::SequencedTaskRunner> task_runner_;
 
+  // The timer and the BITS interface pointers have thread affinity. These
+  // members are initialized on the FILE thread and they must be destroyed
+  // on the FILE thread.
   scoped_ptr<base::RepeatingTimer<BackgroundDownloader> > timer_;
 
   base::win::ScopedComPtr<IBackgroundCopyManager> bits_manager_;
diff --git a/chrome/browser/component_updater/component_updater_service.cc b/chrome/browser/component_updater/component_updater_service.cc
index 780354b..2095c05 100644
--- a/chrome/browser/component_updater/component_updater_service.cc
+++ b/chrome/browser/component_updater/component_updater_service.cc
@@ -155,8 +155,8 @@
 // the tasks. Also when we do network requests there is only one |url_fetcher_|
 // in flight at a time.
 // There are no locks in this code, the main structure |work_items_| is mutated
-// only from the UI thread. The unpack and installation is done in the file
-// thread and the network requests are done in the IO thread and in the file
+// only from the UI thread. The unpack and installation is done in a blocking
+// pool thread. The network requests are done in the IO thread or in the file
 // thread.
 class CrxUpdateService : public ComponentUpdateService {
  public: