For an edge case like the following in sloppy mode
  with ({}) function f() {}
a lexical scope needs to be created around the body in order
to hold the function declaration, so it can be hoisted according
to a loose interpretation of Annex B 3.3 (loose because ES2015
does not permit a function declaration as the body of a with
statement). This patch adds that scope.

BUG=chromium:542100
LOG=N
R=adamk

Review URL: https://codereview.chromium.org/1404803002

Cr-Commit-Position: refs/heads/master@{#31269}