Implement FetchClientSettingsObject::GetHttpsState()

Previously, FetchClientSettingsObjectImpl
- Is used as WorkerFetchContext's FetchClientSettingsObject,
- Implements GetHttpsState(), and
- Is used for checking mixed contents on workers.

Issue 880027 will introduce outsideSettings WorkerFetchContext
which will have FetchClientSettingsObjectSnapshot as its
FetchClientSettingsObject [1].

Therefore, this CL switches
- WorkerFetchContext's FetchClientSettingsObject and
- MixedContentChecker::IsMixedContent()
to use FetchClientSettingsObject (not ...Impl), and
implements GetHttpsState() in FetchClientSettingsObject
and FetchClientSettingsObjectSnapshot.

This CL shouldn't change the behavior at this time, because
WorkerFetchContext's FetchClientSettingsObject is still
a FetchClientSettingsObjectImpl object, and thus mixed content
checks is done using already-implemented
FetchClientSettingsObjectImpl::GetHttpsState().

The code path added in this CL will be used in [2].

[1] https://chromium-review.googlesource.com/1328043
[2] https://chromium-review.googlesource.com/1328164

Bug: 880027
Change-Id: I399694bd239c21fe9b5a650fcb689fb2c98572f5
Reviewed-on: https://chromium-review.googlesource.com/c/1328162
Reviewed-by: Hiroki Nakagawa <nhiroki@chromium.org>
Reviewed-by: Mike West <mkwst@chromium.org>
Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Commit-Queue: Hiroshige Hayashizaki <hiroshige@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607860}
12 files changed