This adds support to specify the maximum memory size when building a
WebAssembly module. Default is not maximum, one can be explicitly set.
It is mainly used by the WebAssembly fuzzers to prevent OOMs.

R=ahaas@chromium.org
BUG=chromium:759973

Change-Id: Ibf5fa63a7e36e5f3b65ced528c73a65355d5632f
Reviewed-on: https://chromium-review.googlesource.com/640386Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47676}