Disable a flaky test DownloadContentTest.DownloadCancelled on more platforms

Bug: 754679
Change-Id: Icabfdc8f753595cd9b586b721ac58c607e7b660d
Tbr: qinmin@chromium.org
Reviewed-on: https://chromium-review.googlesource.com/778646Reviewed-by: Takeshi Yoshino <tyoshino@chromium.org>
Commit-Queue: Takeshi Yoshino <tyoshino@chromium.org>
Cr-Commit-Position: refs/heads/master@{#517777}

content/browser/download/download_browsertest.cc

@@ -913,13 +913,8 @@ class ParallelDownloadTest : public DownloadContentTest {
 
 }  // namespace
 
-#if defined(OS_ANDROID)
-// Failing/Flaky on Android: https://crbug.com/754679
-#define MAYBE_DownloadCancelled DISABLED_DownloadCancelled
-#else
-#define MAYBE_DownloadCancelled DownloadCancelled
-#endif
-IN_PROC_BROWSER_TEST_F(DownloadContentTest, MAYBE_DownloadCancelled) {
+// Flaky. See https://crbug.com/754679.
+IN_PROC_BROWSER_TEST_F(DownloadContentTest, DISABLED_DownloadCancelled) {
   SetupEnsureNoPendingDownloads();
 
   // Create a download, wait until it's started, and confirm