[Sheriff] Disable fast/harness/internals-observe-gc.html.

Disable
fast/harness/internals-observe-gc.html
in Win10 (failure).

TBR=shimazu@chromium.org

Bug: 1003268
Change-Id: I4673f88ed08c2ec40a0e48835072c155e041682d
No-try: true
No-Presubmit: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1800406Reviewed-by: vitaliii <vitaliii@chromium.org>
Commit-Queue: vitaliii <vitaliii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#695969}

third_party/blink/web_tests/TestExpectations

@@ -6219,3 +6219,6 @@ crbug.com/1003055 virtual/threaded/external/wpt/css/css-scroll-snap/scroll-targe
 crbug.com/1003055 virtual/threaded/external/wpt/css/css-scroll-snap/scroll-target-snap-001.html [ Failure ]
 crbug.com/1003055 virtual/threaded/external/wpt/css/css-scroll-snap/scroll-target-snap-002.html [ Failure ]
 crbug.com/1003055 virtual/threaded/external/wpt/css/css-scroll-snap/scroll-target-snap-003.html [ Failure ]
+
+# Sheriff 2019-09-12
+crbug.com/1003268 [ Win10 ] fast/harness/internals-observe-gc.html [ Failure ]