Fix crash in update_client::BackgroundDownloader::EndDownload.

components/update_client/background_downloader_win.cc

Index: components/update_client/background_downloader_win.cc
diff --git a/components/update_client/background_downloader_win.cc b/components/update_client/background_downloader_win.cc
index 4361536dfecd35c2f40001b9eef67f29d5e53516..ea0b0ab440d121432d3b48e701460ad8b76bc393 100644
--- a/components/update_client/background_downloader_win.cc
+++ b/components/update_client/background_downloader_win.cc
@@ -444,6 +444,10 @@ void BackgroundDownloader::OnTimer() {
       base::Bind(&BackgroundDownloader::OnDownloading, base::Unretained(this)));
 }
 
+bool BackgroundDownloader::TimerIsRunning() const {
+  return timer_.get() && timer_->IsRunning();
+}
+
 void BackgroundDownloader::DoStartDownload(const GURL& url) {
   DCHECK(thread_checker_.CalledOnValidThread());
   task_runner()->PostTask(FROM_HERE,
@@ -566,7 +570,7 @@ void BackgroundDownloader::OnDownloading() {
 void BackgroundDownloader::EndDownload(HRESULT error) {
   DCHECK(task_runner()->RunsTasksOnCurrentThread());
 
-  DCHECK(!timer_->IsRunning());
+  DCHECK(!TimerIsRunning());
 
   const base::Time download_end_time(base::Time::Now());
   const base::TimeDelta download_time =