Make DetachableProperties::IsDetached() reflect the underlying property

After this CL, DetachableProperties::IsDetached() returns
the underlying ResourceFetcherProperties::IsDetached() before
Detach() is called,
while it has been returning always false before Detach().

This is consistent with that NullResourceFetcherProperties::IsDetached()
can be true without any detaching.

This CL changes the IsDetached() value to true when the underlying
ResourceFetcherProperties is NullResourceFetcherProperties,
e.g. in XHR's responseXML.

Bug: 914739
Change-Id: I3878850a20c552bcf83dc0f3769b76e7cb079d04
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1583579
Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Commit-Queue: Hiroshige Hayashizaki <hiroshige@chromium.org>
Cr-Commit-Position: refs/heads/master@{#653908}
1 file changed