Annotate reason for failing test ProxySettingsApiTest.ProxyEventsInvalidProxy.

Bug: 876568
Cq-Include-Trybots: luci.chromium.try:linux_mojo
Change-Id: I30ca8030e94f34245d4d53dfc25a463d66bca00e
Reviewed-on: https://chromium-review.googlesource.com/1185462Reviewed-by: Matt Mueller <mattm@chromium.org>
Commit-Queue: Eric Roman <eroman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#585198}

testing/buildbot/filters/mojo.fyi.network_browser_tests.filter

@@ -6,7 +6,6 @@
 # See https://crbug.com/769401
 
 # Uncategorized timeouts or test failures.
--ProxySettingsApiTest.ProxyEventsInvalidProxy
 -RegisterProtocolHandlerBrowserTest.CustomHandler
 
 # Domain Reliability has yet to be hookup to the NetworkService.
@@ -99,6 +98,10 @@
 # Extension listeners for "chrome.proxy.onProxyError" are not called for errors
 # in PAC scripts.
 -ProxySettingsApiTest.ProxyEventsParseError
+# https://crbug.com/876568
+# Extension listeners for "chrome.proxy.onProxyError" are not called for
+# failures connecting to proxy.
+-ProxySettingsApiTest.ProxyEventsInvalidProxy
 
 # https://crbug.com/827582
 # Editing response cookies through headers with webRequest is not supported with