While they have not been observed to slow down real-world use cases,
some blink_layout microbenchmarks feel better with these methods
disabled. In order to be concervative at the launch time, lift
the CFI defense for these methods.

8/10 of these methods will become much faster when an optimization
proposed in https://crbug.com/638056 -- we only need to load vptr
once (before the loop) and have a single CFI check instead of
a check per iteration.

BUG=638056,634139

Review-Url: https://codereview.chromium.org/2258003002
Cr-Commit-Position: refs/heads/master@{#38759}