Update TestExpectation for mouse-scrolling-on-div-scrollbar-thumb.html

This test passes on several bots but is marked as Crash only. Update
the expectation accordingly.

https://test-results.appspot.com/dashboards/flakiness_dashboard.html#testType=webkit_layout_tests%20(with%20patch)&tests=virtual/compositor_threaded_scrollbar_scrolling/fast/scrolling/scrollbars/mouse-scrolling-on-div-scrollbar-thumb.html

TBR=bokan@chromium.org

Bug: 979408
Change-Id: I12d30310e567f08b3093236a9a098fd5d41074b3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2024538Reviewed-by: Yi Gu <yigu@chromium.org>
Commit-Queue: Yi Gu <yigu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#735915}

third_party/blink/web_tests/TestExpectations

@@ -2601,7 +2601,7 @@ crbug.com/1009892 [ Mac ] virtual/compositor_threaded_scrollbar_scrolling_hidpi/
 # These cause a violation of a DCHECK in CC by sending a GestureScrollBegin
 # without closing an existing one.
 crbug.com/979408 virtual/compositor_threaded_scrollbar_scrolling/fast/scrolling/scrollbars/mouse-autoscrolling-on-scrollbar.html [ Crash Failure Timeout ]
-crbug.com/979408 virtual/compositor_threaded_scrollbar_scrolling/fast/scrolling/scrollbars/mouse-scrolling-on-div-scrollbar-thumb.html [ Crash ]
+crbug.com/979408 virtual/compositor_threaded_scrollbar_scrolling/fast/scrolling/scrollbars/mouse-scrolling-on-div-scrollbar-thumb.html [ Pass Crash Timeout ]
 
 # Some control characters still not visible
 crbug.com/893490 [ Mac ] external/wpt/css/css-text/white-space/control-chars-001.html [ Failure ]