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There has been a discrepancy between how the subresource filter and the rest of
Safe Browsing defines the meaning of `redirect urls`. For the redirect chain A
-> B -> C, the SafeBrowsingResourceThrottle considers A as the |original_url|
and [B, C] as |redirect_urls|.  In contrast, the subresource filter expects C
as the resource URL and [A, B] as redirect URLs.

This CL performs the correct transformation on the |redirect_urls| list before
passing it from the SafeBrowsingResourceThrottle to the subresource filter.
Plus, it also avoid calling out to the ContentSubresourceFilterDriverFactory in
case the unsafe resource is not a main frame document.

BUG=646800,609747

Review-Url: https://codereview.chromium.org/2339733003
Cr-Commit-Position: refs/heads/master@{#419373}