Mark test as flaky

Bug: 786995
Change-Id: Ifd48a214d84503e571abd6da6884dd17cfa90a3b
Reviewed-on: https://chromium-review.googlesource.com/779639Reviewed-by: Fernando Serboncini <fserb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#517849}

third_party/WebKit/LayoutTests/TestExpectations

@@ -1924,6 +1924,7 @@ crbug.com/624430 [ Win10 ] fast/text/font-features/caps-casemapping.html [ Failu
 crbug.com/620432 accessibility/aria-activedescendant.html [ Failure ]
 
 crbug.com/399507 virtual/threaded/http/tests/devtools/tracing/timeline-paint/layer-tree.js [ Skip ]
+crbug.com/786995 virtual/threaded/http/tests/devtools/tracing/timeline-style/timeline-style-recalc-all-invalidator-types.js [ Pass Failure ]
 
 crbug.com/636424 [ Win7 Debug ] editing/selection/modify_move/move-by-word-visually-crash-test-5.html [ Pass Timeout ]
 crbug.com/638618 http/tests/devtools/editor/text-editor-search-switch-editor.js [ Skip ]