Network Service: clarify XSDB comment in network_content_browsertests.filter

Bug: 792546, 786505
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_mojo
Change-Id: Id8ff7999115ca602c929b8c8e691121894ed94b7
Reviewed-on: https://chromium-review.googlesource.com/811744Reviewed-by: Charlie Reis <creis@chromium.org>
Commit-Queue: Nick Carter <nick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#522179}

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

@@ -124,7 +124,9 @@
 -ResourceDispatcherHostBrowserTest.SniffHTMLWithNoContentType
 -ResourceDispatcherHostBrowserTest.SniffNoContentTypeNoData
 
-# Some new/changed tests for crbug.com/786505 are failing.
+# Cross-site document blocking needs to be implemented in the network service.
+# https://crbug.com/786505 (cross site document blocking)
+# https://crbug.com/792546 (cross site document blocking in network service)
 -SiteIsolationStatsGathererBrowserTest/SiteIsolationStatsGathererBrowserTest.CrossSiteDocumentBlockingForMimeType/0
 -SiteIsolationStatsGathererBrowserTest/SiteIsolationStatsGathererBrowserTest.CrossSiteDocumentBlockingForMimeType/1
 -CrossSiteDocumentBlockingTest.BlockDocuments