Port a971a64d

Original Commit Message:

    We can remove a lot of native code and rely on CallOrConstructVarargs
    to do the stack manipulation for us.

    This will also take advantage of the fast-path for double arrays in
    CallOrConstructDoubleVarargs.

    We can also remove Runtime_SpreadIterableFixed because it isn't used
    anymore. We just call directly into spread_iterable from CSA.

R=petermarshall@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=
LOG=N

Change-Id: Idad830c9aace4151db866c9f863158cd7525e881
Reviewed-on: https://chromium-review.googlesource.com/546575Reviewed-by: Joran Siu <joransiu@ca.ibm.com>
Commit-Queue: Jaideep Bajwa <bjaideep@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#46187}