Override IsRedirectResponse in extension protocols

The default URLFileRequestJob::IsRedirectResponse implementation is incorrect
for URLRequestExtensionJob (chrome-extension:-scheme) and ExtensionResourcesJob (chrome-extension-resource:-scheme).

BUG=388852,424961

Review URL: https://codereview.chromium.org/650453003

Cr-Commit-Position: refs/heads/master@{#300329}
(cherry picked from commit 54a4e4044b90ab88d59af098586cd82bc1cfac8e)

Review URL: https://codereview.chromium.org/702673003

Cr-Commit-Position: refs/branch-heads/2125@{#598}
Cr-Branched-From: b68026d94bda36dd106a3d91a098719f952a9477-refs/heads/master@{#290040}
2 files changed