Port 28261daa

Original commit message:
    This operator now provides a second output which indicates whether the
    conversion from float32 to int64 was successful or not. The second output
    returns 0 if the conversion fails, or something else if the conversion succeeds.

    The second output can be ignored, which means that the operator can be used the
    same as the original operator.

R=ahaas@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1530273002

Cr-Commit-Position: refs/heads/master@{#32914}