[Fetch] Default value of FetchAPIResponse.response_type should be kDefault rather than kOpaque

This is according to the spec:
https://fetch.spec.whatwg.org/#concept-response-type

BUG=911930

Change-Id: I3f73220f2878dd7a7de9e9c6c4b7af0b54d99840
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1611136
Commit-Queue: Kinuko Yasuda <kinuko@chromium.org>
Auto-Submit: Leon Han <leon.han@intel.com>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Cr-Commit-Position: refs/heads/master@{#659384}
1 file changed