Update layout test expectations for some flaky tests.

virtual/rootlayerscrolls/scrollbars/custom-scrollbar-inactive-pseudo.html
virtual/prefer_compositing_to_lcd_text/scrollbars/custom-scrollbar-inactive-pseudo.html
virtual/prefer_compositing_to_lcd_text/scrollbars/custom-scrollbar-adjust-on-inactive-pseudo.html
are flaky on Linux as well

virtual/gpu-rasterization/images/image-hover-display-alt.html is flaky

TBR=avi@chromium.org
NOTRY=true

Bug: 789567, 789478, 790025
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_mojo
Change-Id: I6f52e55a3a3a4573750d971f1ce7247448579061
Reviewed-on: https://chromium-review.googlesource.com/801256
Commit-Queue: John Abd-El-Malek <jam@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Cr-Commit-Position: refs/heads/master@{#520942}

third_party/WebKit/LayoutTests/FlagExpectations/enable-features=NetworkService

@@ -176,7 +176,6 @@ Bug(none) http/tests/websocket/httponly-cookie.pl [ Failure ]
 Bug(none) http/tests/xmlhttprequest/xmlhttprequest-data-url.html [ Failure ]
 Bug(none) http/tests/devtools/sources/debugger-breakpoints/event-listener-breakpoints-xhr.js [ Timeout ]
 Bug(none) plugins/iframe-plugin-bgcolor.html [ Timeout ]
-Bug(none) virtual/gpu/fast/canvas/OffscreenCanvas-2d-imageSmoothing-in-worker.html [ Pass Timeout ]
 Bug(none) virtual/mouseevent_fractional/fast/events/attribute-listener-cloned-from-frameless-doc.xhtml [ Timeout ]
 
 # Plugin throttle is not implemented.

third_party/WebKit/LayoutTests/TestExpectations

@@ -3830,14 +3830,15 @@ crbug.com/789139 [ Linux ] http/tests/devtools/sources/debugger/live-edit-no-rev
 crbug.com/789139 [ Linux ] virtual/mojo-loading/http/tests/devtools/sources/debugger/live-edit-no-reveal.js [ Pass Failure ]
 crbug.com/785179 [ Mac10.11 ] http/tests/devtools/console/console-viewport-stick-to-bottom.js [ Pass Failure ]
 # Sheriff failures 2017-11-29
-crbug.com/789567 [ Mac ] virtual/rootlayerscrolls/scrollbars/custom-scrollbar-inactive-pseudo.html [ Failure Pass ]
-crbug.com/789567 [ Mac ] virtual/rootlayerscrolls/scrollbars/custom-scrollbar-adjust-on-inactive-pseudo.html [ Failure Pass ]
-crbug.com/789567 [ Mac ] virtual/prefer_compositing_to_lcd_text/scrollbars/custom-scrollbar-inactive-pseudo.html [ Failure Pass ]
-crbug.com/789478 [ Mac ] virtual/prefer_compositing_to_lcd_text/scrollbars/custom-scrollbar-adjust-on-inactive-pseudo.html [ Pass Failure ]
+crbug.com/789567 virtual/rootlayerscrolls/scrollbars/custom-scrollbar-inactive-pseudo.html [ Failure Pass ]
+crbug.com/789567 virtual/rootlayerscrolls/scrollbars/custom-scrollbar-adjust-on-inactive-pseudo.html [ Failure Pass ]
+crbug.com/789567 virtual/prefer_compositing_to_lcd_text/scrollbars/custom-scrollbar-inactive-pseudo.html [ Failure Pass ]
+crbug.com/789478 virtual/prefer_compositing_to_lcd_text/scrollbars/custom-scrollbar-adjust-on-inactive-pseudo.html [ Pass Failure ]
 crbug.com/789533 virtual/gpu/fast/canvas/OffscreenCanvas-2d-imageSmoothing.html [ Pass Failure ]
 # Sheriff failures 2017-11-30
 crbug.com/789921 [ Win7 ] media/video-controls-overflow-menu-last-button-visible.html [ Pass Failure ]
 crbug.com/789111 virtual/pwa-full-code-cache/http/tests/devtools/service-workers/service-worker-v8-cache.js [ Pass Failure ]
+crbug.com/790025 virtual/gpu-rasterization/images/image-hover-display-alt.html [ Failure Pass ]
 
 # These tests fail often on Linux. https://crbug.com/790549
 crbug.com/788390 [ Linux ] http/tests/media/autoplay/document-user-activation-cross-origin-feature-policy-delegation.html [ Failure Pass Timeout ]