sheriff: disable DeclarativeNetRequestBrowserTest.BlockRequests_UrlFilter

This test flakily times out on Mac debug - even successful runs regularly
take 30-40 seconds.

Bug: 900447
Change-Id: I9d8710c5329ad4de30ff1d9913288b2b034acd7d
Tbr: kelvinjiang@chromium.org
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2264912
Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Commit-Queue: Elly Fong-Jones <ellyjones@chromium.org>
Cr-Commit-Position: refs/heads/master@{#781958}
diff --git a/chrome/browser/extensions/api/declarative_net_request/declarative_net_request_browsertest.cc b/chrome/browser/extensions/api/declarative_net_request/declarative_net_request_browsertest.cc
index 6e7bbe0..8da86f8c 100644
--- a/chrome/browser/extensions/api/declarative_net_request/declarative_net_request_browsertest.cc
+++ b/chrome/browser/extensions/api/declarative_net_request/declarative_net_request_browsertest.cc
@@ -709,8 +709,9 @@
 using DeclarativeNetRequestBrowserTest_Unpacked =
     DeclarativeNetRequestBrowserTest;
 
-#if defined(OS_WIN) && !defined(NDEBUG)
+#if (defined(OS_WIN) || defined(OS_MACOSX)) && !defined(NDEBUG)
 // TODO: test times out on win7-debug. http://crbug.com/900447.
+// Also times out on mac-debug: https://crbug.com/900447
 #define MAYBE_BlockRequests_UrlFilter DISABLED_BlockRequests_UrlFilter
 #else
 #define MAYBE_BlockRequests_UrlFilter BlockRequests_UrlFilter