- Currently WebAssembly.Memory.grow() assumes that it always has an instance associated with it,
 fix to grow and reflect new size when no instance is associated with memory object.
 - Correctness fixes for the js api, throw range errors instead of generic errors

BUG=chromium:680938

R=bradnelson@chromium.org, titzer@chromium.org

Review-Url: https://codereview.chromium.org/2638243002
Cr-Commit-Position: refs/heads/master@{#42432}