Update CFI blacklist to match the recent renames in Blink.

In particular, it's a follow up to
https://chromium-review.googlesource.com/472192.

This CL is just to fix the bots. I will follow up with proper
changes to the allocator which will eliminate the need for the
blacklist entry.

BUG=713293

Review-Url: https://codereview.chromium.org/2834513002
Cr-Commit-Position: refs/heads/master@{#465728}

tools/cfi/blacklist.txt

 # e.g. RolloverProtectedTickClock
 fun:*MutableInstance*
 
-# WTF allocators.
-fun:*allocate*Backing*
+# WTF allocators. See https://crbug.com/713293.
+fun:*Allocate*Backing*
 
 # WTF::ThreadSpecific
 fun:*ThreadSpecific*