- Removes TODO implying that moving a 32 bit immediate to a stack slot
  doesn't require the use of kScratchRegister. While movl can be used
  to store a 32 bit immediate to memory, it doesn't zero extend leaving
  part of the slot uninitialized.

Bug: 
Change-Id: I0ebc873b752d508753b624e0b5e262193a568c2b
Reviewed-on: https://chromium-review.googlesource.com/784193Reviewed-by: Mircea Trofin <mtrofin@chromium.org>
Commit-Queue: Bill Budge <bbudge@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49592}