There's no need to check IsLexicalVariableMode since it's subsumed
by binding_needs_init.

Drive-by change: in VisitVariableLoad, move SetResultInAccumulator
out of switch cases.

BUG=

Review-Url: https://codereview.chromium.org/2232313002
Cr-Commit-Position: refs/heads/master@{#38590}