Port 98d7b23e

Original Commit Message:

    This uses a WebAssembly runtime stub for the out-of-line {DoubleToI}
    computation instead of a builtin specific to a certain Isolate. It is
    another step towards making {WasmCode} independent of the Isolate.

R=mstarzinger@chromium.org, joransiu@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=v8:7424
LOG=N

Change-Id: I2f78432134ea150bb00bea339a6e71c11aa625b0
Reviewed-on: https://chromium-review.googlesource.com/1099877Reviewed-by: Joran Siu <joransiu@ca.ibm.com>
Commit-Queue: Junliang Yan <jyan@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#53723}