Printing an asm.js success message and timings is useful,
but also non-deterministic. Making the message stable unless a flag is passed.
This will avoid making it a hassle in the future to create LayoutTests
that use asm.js and verify console output.

BUG=v8:4203
R=titzer@chromium.org

Review-Url: https://codereview.chromium.org/2574273002
Cr-Commit-Position: refs/heads/master@{#41700}