port 240b7db9 (r34630)

  original commit message:
  I implemented I64ShrU and I64ShrS the same as I64Shl in https://codereview.chromium.org/1756863002

BUG=

Review URL: https://codereview.chromium.org/1783703003

Cr-Commit-Position: refs/heads/master@{#34656}