[Sheriff] Disable flaky DownloadExtensionTest

This tast have been increasingly flaky on ASAN/LSAN builders
for the recent few days:
https://ci.chromium.org/p/chromium/builders/ci/Linux%20ASan%20LSan%20Tests%20%281%29

TBR=eugenebut@chromium.org

Bug: 1114226
Change-Id: I549b6caef3046e36da64da5010179e965b6e8fbb
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2348928
Commit-Queue: Anatoliy Potapchuk <apotapchuk@chromium.org>
Reviewed-by: Anatoliy Potapchuk <apotapchuk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#796750}

chrome/browser/extensions/api/downloads/downloads_api_browsertest.cc

@@ -3877,9 +3877,17 @@ IN_PROC_BROWSER_TEST_F(
                           result_id)));
 }
 
+// This test is flaky on Linux ASan LSan Tests bot. https://crbug.com/1114226
+#if defined(OS_LINUX) && defined(ADDRESS_SANITIZER)
+#define MAYBE_DownloadExtensionTest_OnDeterminingFilename_IncognitoSplit \
+  DISABLED_DownloadExtensionTest_OnDeterminingFilename_IncognitoSplit
+#else
+#define MAYBE_DownloadExtensionTest_OnDeterminingFilename_IncognitoSplit \
+  DownloadExtensionTest_OnDeterminingFilename_IncognitoSplit
+#endif
 IN_PROC_BROWSER_TEST_F(
     DownloadExtensionTest,
-    DownloadExtensionTest_OnDeterminingFilename_IncognitoSplit) {
+    MAYBE_DownloadExtensionTest_OnDeterminingFilename_IncognitoSplit) {
   LoadExtension("downloads_split");
   ASSERT_TRUE(StartEmbeddedTestServer());
   std::string download_url = embedded_test_server()->GetURL("/slow?0").spec();