Update SlowTests: some xmlhttprequest/timeout tests are Slow

These tests are Slow not only on Mac10.13, but in general.
Let me update the entry not to be Mac10.13 specific, and
not to be virtual/outofblink-cors(-ns) specific.

Bug: 869800
Change-Id: I76f13714b93b314a14c16dae5e110a841547d92c
Reviewed-on: https://chromium-review.googlesource.com/1160136Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Commit-Queue: Takashi Toyoshima <toyoshim@chromium.org>
Cr-Commit-Position: refs/heads/master@{#580134}

third_party/WebKit/LayoutTests/SlowTests

@@ -422,7 +422,16 @@ crbug.com/866850 [ Linux Mac ] virtual/gpu/fast/canvas/color-space/canvas-create
 crbug.com/866850 [ Linux Mac ] virtual/gpu/fast/canvas/OffscreenCanvas-filter.html [ Slow ]
 crbug.com/866850 [ Linux Mac ] virtual/gpu/fast/canvas/OffscreenCanvas-filter-in-worker.html [ Slow ]
 
-crbug.com/869662 [ Mac10.13 ] virtual/outofblink-cors-ns/http/tests/xmlhttprequest/timeout/xmlhttprequest-timeout-worker-simple.html [ Slow ]
-crbug.com/869662 [ Mac10.13 ] virtual/outofblink-cors-ns/http/tests/xmlhttprequest/timeout/xmlhttprequest-timeout-worker-synconworker.html [ Slow ]
-crbug.com/869662 [ Mac10.13 ] virtual/outofblink-cors/http/tests/xmlhttprequest/timeout/xmlhttprequest-timeout-worker-aborted.html [ Slow ]
+### Some timeout tests in xmlhttprequest/timeout/ are slow
+crbug.com/869800 http/tests/xmlhttprequest/timeout/xmlhttprequest-timeout-worker-aborted.html [ Slow ]
+crbug.com/869800 http/tests/xmlhttprequest/timeout/xmlhttprequest-timeout-worker-simple.html [ Slow ]
+crbug.com/869800 http/tests/xmlhttprequest/timeout/xmlhttprequest-timeout-worker-synconworker.html [ Slow ]
+crbug.com/869800 virtual/outofblink-cors-ns/http/tests/xmlhttprequest/timeout/xmlhttprequest-timeout-worker-aborted.html [ Slow ]
+crbug.com/869800 virtual/outofblink-cors-ns/http/tests/xmlhttprequest/timeout/xmlhttprequest-timeout-worker-simple.html [ Slow ]
+crbug.com/869800 virtual/outofblink-cors-ns/http/tests/xmlhttprequest/timeout/xmlhttprequest-timeout-worker-synconworker.html [ Slow ]
+crbug.com/869800 virtual/outofblink-cors/http/tests/xmlhttprequest/timeout/xmlhttprequest-timeout-worker-aborted.html [ Slow ]
+crbug.com/869800 virtual/outofblink-cors/http/tests/xmlhttprequest/timeout/xmlhttprequest-timeout-worker-simple.html [ Slow ]
+crbug.com/869800 virtual/outofblink-cors/http/tests/xmlhttprequest/timeout/xmlhttprequest-timeout-worker-synconworker.html [ Slow ]
+
+### Slow only on Mac10.13
 crbug.com/869662 [ Mac10.13 ] virtual/threaded/fast/scrolling/overflow-scrollability.html [ Slow ]

third_party/WebKit/LayoutTests/TestExpectations

@@ -4865,6 +4865,5 @@ crbug.com/869364 virtual/gpu/fast/canvas/OffscreenCanvas-filter.html [ Pass Time
 
 # Sheriff 2018-08-01
 crbug.com/869773 [ Mac Linux ] http/tests/misc/window-dot-stop.html [ Pass Failure ]
-crbug.com/869800 [ Mac Release ] virtual/outofblink-cors/http/tests/xmlhttprequest/timeout/xmlhttprequest-timeout-worker-aborted.html [ Pass Timeout ]
 crbug.com/869829 [ Mac Release ] http/tests/media/video-cancel-load.html [ Pass Failure ]
 crbug.com/862806 [ Linux ] css3/filters/effect-drop-shadow-hw.html [ Pass Timeout ]