LayoutTests: timer-throttling-hidden-page.html is flaky on all platforms.

BUG=520170
TBR=skyostil@chromium.org,dpranke@chromium.org,mcgreevy@chromium.org,qyearsley@chromium.org,jeffcarp@chromium.org
NOTRY=true

Review-Url: https://codereview.chromium.org/2956573002
Cr-Commit-Position: refs/heads/master@{#481811}

third_party/WebKit/LayoutTests/TestExpectations

@@ -797,7 +797,7 @@ crbug.com/522648 fast/events/touch/compositor-touch-hit-rects-iframes.html [ Cra
 crbug.com/521858 [ Win7 ] http/tests/security/media-element-audio-source-node-same-origin.html [ Failure Pass ]
 crbug.com/521858 [ Win7 ] virtual/mojo-loading/http/tests/security/media-element-audio-source-node-same-origin.html [ Failure Pass ]
 crbug.com/521853 [ Win ] http/tests/inspector/search/sources-search-scope.html [ Failure Pass ]
-crbug.com/520170 [ Win ] fast/dom/timer-throttling-hidden-page.html [ Failure Pass ]
+crbug.com/520170 fast/dom/timer-throttling-hidden-page.html [ Failure Pass ]
 crbug.com/652536 fast/events/mouse-cursor-change-after-image-load.html [ Failure Pass ]
 crbug.com/520188 [ Win ] http/tests/local/fileapi/file-last-modified-after-delete.html [ Failure Pass ]
 crbug.com/520188 [ Win ] virtual/mojo-loading/http/tests/local/fileapi/file-last-modified-after-delete.html [ Failure Pass ]