Disable a flaky Background Fetch browser test.

NOTRY=true

Bug: 822276
Change-Id: I7a1781912c47be7bd34cf39e2f1b6f0610cf281a
Reviewed-on: https://chromium-review.googlesource.com/964561
Commit-Queue: Mugdha Lakhani <nator@chromium.org>
Reviewed-by: Peter Beverloo <peter@chromium.org>
Reviewed-by: Anita Woodruff <awdf@chromium.org>
Cr-Commit-Position: refs/heads/master@{#543424}

chrome/browser/background_fetch/background_fetch_browsertest.cc

@@ -273,7 +273,9 @@ class BackgroundFetchBrowserTest : public InProcessBrowserTest {
   DISALLOW_COPY_AND_ASSIGN(BackgroundFetchBrowserTest);
 };
 
-IN_PROC_BROWSER_TEST_F(BackgroundFetchBrowserTest, DownloadService_Acceptance) {
+// Flaky. See https://crbug.com/822276
+IN_PROC_BROWSER_TEST_F(BackgroundFetchBrowserTest,
+                       DISABLED_DownloadService_Acceptance) {
   // Starts a Background Fetch for a single to-be-downloaded file and waits for
   // that request to be scheduled with the Download Service.