Port 95844d94

Original commit message:
    The new operator provides a second output which indicates whether the
    conversion from float64 to int64 was successful or not. The second
    output returns 0 if the conversion fails. If the conversion succeeds,
    then the second output is differs from 0.

    The second output can be ignored, which means that the operator can be
    used the same way 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/1515603002

Cr-Commit-Position: refs/heads/master@{#32724}