Require FetchClientSettingsObject in FetchContext ctor

This CL clarifies that a FetchClientSettingsObject is given
to FetchContext at construction by
adding FetchClientSettingsObject parameter to the ctor and
removing SetFetchClientSettingsObject() calls unless
necessary for navigation/detached FrameFetchContext.

This CL also removes
- MockFetchContext::Create()
- MockFetchContext::SetSecurityOrigin()
and adjusted how FetchContext is created in unit tests.

Bug: 880027
Change-Id: I27c7e2718a89ec0ef3a936f3fe6984f1cc97b0a7
Reviewed-on: https://chromium-review.googlesource.com/c/1378820
Commit-Queue: Hiroshige Hayashizaki <hiroshige@chromium.org>
Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Cr-Commit-Position: refs/heads/master@{#617665}
22 files changed