[Chromium sheriff] Mark test flaky on linux: zoom-responsive-transform-animation.html

TBR=ericwilligers@chromium.org

Bug: 750549
Change-Id: If67efe435530c714a3960c928a6e7c5bd71ca40e
Reviewed-on: https://chromium-review.googlesource.com/593376Reviewed-by: meade_UTC10 <meade@chromium.org>
Commit-Queue: meade_UTC10 <meade@chromium.org>
Cr-Commit-Position: refs/heads/master@{#490715}

third_party/WebKit/LayoutTests/TestExpectations

@@ -1180,7 +1180,8 @@ crbug.com/528062 [ Win ] virtual/mojo-loading/http/tests/security/xssAuditor/chu
 
 crbug.com/392706 virtual/threaded/animations/play-state-initially-paused.html [ Failure ]
 
-crbug.com/743009 [ Win ] virtual/threaded/animations/responsive/zoom-responsive-transform-animation.html [ Pass Timeout ]
+# Added Linux in crbug.com/750549
+crbug.com/743009 [ Linux Win ] virtual/threaded/animations/responsive/zoom-responsive-transform-animation.html [ Pass Timeout ]
 
 # Part of a larger issue referenced in the bug. This specific issue will be fixed shortly.
 crbug.com/408159 accessibility/is-ignored-change-sends-notification.html [ Timeout ]