port ac7f0e2b

Original Commit Message:
   *) For all tests the input validation was incorrect, i.e. some values
   were considered invalid although they were valid. The problem was that
   values which are outside int range can get in range through truncation.

   *) Removed an assertion in the x64 code generation of
   TruncateFloat64ToUint32 which trapped on negative inputs.

   *) Introduced a new TF operator TruncateFloat32ToUint32 which does
   the same as ChangeFloat32ToUint32 but does not trap on negative inputs.

R=titzer@chromium.org, ahaas@chromium.org, joransiu@ca.ibm.com, mbrandy@us.ibm.com, michael_dawson@ca.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1844053005

Cr-Commit-Position: refs/heads/master@{#35207}