[DNR] Disable OnRulesMatchedDebug API test for flakiness

Once again this flakes, at the exact same sub-test as well. Will need
further investigation.

Bug: 1087765
Change-Id: Ibe431541b835a8e3de613b6006e1526795c0648c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2223652
Auto-Submit: Kelvin Jiang <kelvinjiang@chromium.org>
Commit-Queue: Karan Bhatia <karandeepb@chromium.org>
Reviewed-by: Karan Bhatia <karandeepb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#773834}

chrome/browser/extensions/api/declarative_net_request/declarative_net_request_apitest.cc

@@ -52,7 +52,9 @@ IN_PROC_BROWSER_TEST_F(DeclarativeNetRequestAPItest, DynamicRules) {
   ASSERT_TRUE(RunExtensionTest("dynamic_rules")) << message_;
 }
 
-IN_PROC_BROWSER_TEST_F(DeclarativeNetRequestAPItest, OnRulesMatchedDebug) {
+// TODO(crbug.com/1087765): Disabled due to flakiness.
+IN_PROC_BROWSER_TEST_F(DeclarativeNetRequestAPItest,
+                       DISABLED_OnRulesMatchedDebug) {
   ASSERT_TRUE(RunExtensionTest("on_rules_matched_debug")) << message_;
 }