Mark a layout test as flaky on Linux Release

This test:
virtual/threaded/fast/scroll-behavior/smooth-scroll/mousewheel-scroll-interrupted.html
is flaky under Release as well on Linux.

Please refer to the Chromium flakiness dashboard here:
http://test-results.appspot.com/dashboards/flakiness_dashboard.html#tests=virtual%2Fthreaded%2Ffast%2Fscroll-behavior%2Fsmooth-scroll%2Fmousewheel-scroll-interrupted.html

TBR=ymalik@chromium.org

Review-Url: https://codereview.chromium.org/2156953003
Cr-Commit-Position: refs/heads/master@{#406129}

third_party/WebKit/LayoutTests/TestExpectations

@@ -805,7 +805,7 @@ crbug.com/425345 [ Mac ] fast/text/line-break-after-question-mark.html [ Failure
 
 crbug.com/574283 [ Mac ] virtual/threaded/fast/scroll-behavior/smooth-scroll/mousewheel-scroll-interrupted.html [ Skip ]
 crbug.com/587165 [ Win7 Debug ] virtual/threaded/fast/scroll-behavior/smooth-scroll/mousewheel-scroll-interrupted.html [ Pass Failure ]
-crbug.com/587165 [ Linux Debug ] virtual/threaded/fast/scroll-behavior/smooth-scroll/mousewheel-scroll-interrupted.html [ Pass Failure ]
+crbug.com/587165 [ Linux ] virtual/threaded/fast/scroll-behavior/smooth-scroll/mousewheel-scroll-interrupted.html [ Pass Failure ]
 
 crbug.com/624247 [ Linux Win7 ] virtual/threaded/fast/scroll-behavior/smooth-scroll/track-scroll.html [ Failure Pass ]