- Introduce new helper IsFastJSArrayWithNoCustomIteration.
  - Consolidates all entry array checks...
    - Is a fast array (defers to BranchIfFastJSArray)
    - No possibility that the Array's iteration protocol has been tampered with
- Introduce new BoolT constant helpers Int32TrueConstant and Int32FalseConstant.

Bug: chromium:804176, chromium:804188
Change-Id: I6b08396484682dc680b431ea564a7a28eeab8108
Reviewed-on: https://chromium-review.googlesource.com/883065
Commit-Queue: Peter Wong <peter.wm.wong@gmail.com>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50867}