Re-enable WPT test sandbox-disallow-same-origin

In the record of the flakiness dashboard there is only one
timeout registered (and no failures).  The one timeout was
a particularly bad run on windows debug, and when it
happened there were a lot of other tests timing out. I
find it likely that there was a slow change in that run.

Bug: 626703
Change-Id: I93f6720b08ecbdbff78d838b84c82ccb38dd4a28
Reviewed-on: https://chromium-review.googlesource.com/1133312Reviewed-by: Robert Flack <flackr@chromium.org>
Commit-Queue: Peter Mayo <petermayo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575184}

third_party/WebKit/LayoutTests/TestExpectations

@@ -3496,7 +3496,6 @@ crbug.com/861564 external/wpt/workers/baseurl/alpha/xhr-in-moduleworker.html [ F
 crbug.com/861564 external/wpt/workers/interfaces/WorkerGlobalScope/location/redirect-module.html [ Failure ]
 
 # Other untriaged test failures, timeouts and crashes from newly-imported WPT tests.
-crbug.com/666703 external/wpt/html/browsers/sandboxing/sandbox-disallow-same-origin.html [ Timeout ]
 crbug.com/626703 external/wpt/html/browsers/history/the-location-interface/location-protocol-setter-non-broken.html [ Failure Pass ]
 
 crbug.com/785940 external/wpt/web-animations/timing-model/timelines/document-timelines.html [ Failure Pass ]