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

Now that 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.,

Review URL:

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