Update TestExepctations for flaky compressor test

We missed this line when we add the tail processing change. Let's add
it back in.

Bug: 731518
Change-Id: Id90cade41f311309ef60f049094478de0ad4c19e
Reviewed-on: https://chromium-review.googlesource.com/956318Reviewed-by: Hongchan Choi <hongchan@chromium.org>
Commit-Queue: Hongchan Choi <hongchan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#541883}

third_party/WebKit/LayoutTests/TestExpectations

@@ -3407,3 +3407,6 @@ crbug.com/819683 [ Linux ] paint/invalidation/background/obscured-background-no-
 crbug.com/819851 [ Mac ] paint/invalidation/forms/checkbox-focus-by-mouse-then-keydown.html [ Skip ]
 crbug.com/819851 [ Mac ] paint/invalidation/forms/radio-focus-by-mouse-then-keydown.html [ Skip ]
 crbug.com/819778 [ Linux ] external/wpt/css/cssom-view/interfaces.html [ Pass Timeout ]
+
+# Sheriff 2018-03-08
+crbug.com/731518 [ Win Linux Mac ] webaudio/DynamicsCompressor/dynamicscompressor-clear-internal-state.html [ Failure Pass ]