Disable flaky FeedbackUploaderDispatchTest.500Response on Linux and ChromeOS

Bug: 864797
Change-Id: I4becdf1fcbc4b9cfd9821ad61641753df14e1407
Tbr: afakhry@chromium.org
NoTry: True
Reviewed-on: https://chromium-review.googlesource.com/1141136
Reviewed-by: Xiaocheng Hu <xiaochengh@chromium.org>
Commit-Queue: Xiaocheng Hu <xiaochengh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575869}
diff --git a/components/feedback/feedback_uploader_dispatch_unittest.cc b/components/feedback/feedback_uploader_dispatch_unittest.cc
index 351a07c..1d84403 100644
--- a/components/feedback/feedback_uploader_dispatch_unittest.cc
+++ b/components/feedback/feedback_uploader_dispatch_unittest.cc
@@ -156,7 +156,14 @@
   EXPECT_TRUE(uploader.QueueEmpty());
 }
 
-TEST_F(FeedbackUploaderDispatchTest, 500Response) {
+#if defined(OS_LINUX) || defined(OS_CHROMEOS)
+// Flaky. crbug.com/864797
+#define MAYBE_500Response DISABLED_500Response
+#else
+#define MAYBE_500Response 500Response
+#endif
+
+TEST_F(FeedbackUploaderDispatchTest, MAYBE_500Response) {
   FeedbackUploader::SetMinimumRetryDelayForTesting(kTestRetryDelay);
   FeedbackUploader uploader(
       shared_url_loader_factory(), context(),