Fix a typo in a web platform test for fetch/integrity

The test has succeeded unexpectedly, so this CL also adds an
expectation file.

Bug: 812667
Change-Id: I649a7663c54f83ccb951c5a4bf075b588908b088
Reviewed-on: https://chromium-review.googlesource.com/948184
Commit-Queue: Yutaka Hirano <yhirano@chromium.org>
Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#540789}