TEST=unittests/InstructionSelectorTest.CombineChangeFloat32ToInt32WithRoundFloat32,
     ChangeFloat64ToInt32OfChangeFloat32ToFloat64, TruncateFloat64ToFloat32OfChangeInt32ToFloat64
BUG=

Review URL: https://codereview.chromium.org/1520503002

Cr-Commit-Position: refs/heads/master@{#32969}