Reland "Use resource throttle to implement shouldOverrideUrlLoading, core change"

Now that https://codereview.chromium.org/1381003004/ has landed we can
reland this patch since we now receive a didFinishLoad callback when
the current navigation finishes even in the case where a new navigation
has reached a provisional state.

This reverts commit e5c3091df04749b232359b6ef22938006af840d5.

TBR=palmer@chromium.org,jam@chromium.org
BUG=325351

Review URL: https://codereview.chromium.org/1424263003

Cr-Commit-Position: refs/heads/master@{#358719}
15 files changed