Port a087abb0

Original Commit Message:

    There's not really a point in passing the resume_mode as parameter to
    the ResumeGenerator builtin. Instead we could as well just store the
    mode to the generator object directly.

    immediately so we don't need to move it there later.

R=bmeurer@chromium.org, joransiu@ca.ibm.com, jbarboza@ca.ibm.com
BUG=
LOG=N

Change-Id: I85d064dad444443fa7ba9d6801e32e4048676ceb
Reviewed-on: https://chromium-review.googlesource.com/783792Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Joran Siu <joransiu@ca.ibm.com>
Commit-Queue: Junliang Yan <jyan@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#49588}