[XHR] Use response tainting to calculate CORS-exposed header-name list

XHR uses the same-originness of the request origin and the destination
URL to calculate the CORS-exposed header-name list, which leads to
wrong results with redirects. Use response tainting as specced.

Bug: 959390
Change-Id: Iec448dfe7d2b47d00f0f471391eb7918a1fe7bc4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1598949
Reviewed-by: Takashi Toyoshima <toyoshim@chromium.org>
Commit-Queue: Yutaka Hirano <yhirano@chromium.org>
Cr-Commit-Position: refs/heads/master@{#657626}