Update expectations of imported/wpt/service-workers

As mentioned at https://crbug.com/602693#c17 and https://crbug.com/657869,
'[ Skip ]' in TestExpectations cannot be overwritten by WPTTestExpectations.
This patch changes '[ Skip ]' to '[ Failure ]' by default in TestExpectations
in order to run the w3c tests on WPTServe bots.

BUG=602693,453190,624278,617886,571722,618616
TEST=./third_party/WebKit/Tools/Scripts/run-webkit-tests -f -t Debug imported/wpt/service-workers
TEST=./third_party/WebKit/Tools/Scripts/run-webkit-tests --enable-wptserve -f -t Debug imported/wpt/service-workers

Review-Url: https://codereview.chromium.org/2441963002
Cr-Commit-Position: refs/heads/master@{#427010}
2 files changed