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There are two main fixes:
-use GetWebContentsGetter instead of the RPH/RFH IDs since the latter don't exist for browser side navigation
-switching TabSpecificContentSettings to use the new navigation callbacks. This is needed because with PlzNavigate, the old didstartprovisionalload callback (from the new renderer) would run after the cookie request (from the browser), and so we would wipe out the settings map. Using the new callbacks preserves the order of these callbacks with PlzNavigate.

This fixes the following browser tests with PlzNavigate:
ContentSettingsTest.RedirectCrossOrigin
ContentSettingsTest.RedirectLoopCookies

BUG=504347

Review-Url: https://codereview.chromium.org/2374443003
Cr-Commit-Position: refs/heads/master@{#421224}