The WebAssembly spec requires a HasProperty() check for the maximum
property of the descriptor object which is used to set up a
WebAssembly.Memory object or a WebAssembly.Table object.

The original implementation only approximated the HasProperty() check.
It used Get() to get the value of the maximum property of the descriptor
object and compared the resulting value to {undefined}. However, this
approximation is incorrect if the property exists but its value is
{undefined}.

R=titzer@chromium.org, franzih@chromium.org
BUG=chromium:649461
TEST=mjsunit/wasm/memory

Review-Url: https://codereview.chromium.org/2367673003
Cr-Commit-Position: refs/heads/master@{#39722}