This disables the usage of the {maybe_assigned} flag that the variable
resolution computes for each variable on non-asm.js code. Note that the
analysis is fundamentally broken for destructuring and top-level lexical
variables. Also note that this still uses the analysis for asm.js code
even though it is not validated. One can still trigger the bug by using
invalid constructs within a function marked with "use asm". The fix is
intentionally minimal so that it can be merged to release branches.

R=bmeurer@chromium.org
TEST=mjsunit/regress/regress-crbug-659915
BUG=chromium:659915

Review-Url: https://codereview.chromium.org/2471523005
Cr-Commit-Position: refs/heads/master@{#40716}