The previous code did not properly check for harmony const when
doing the dynamic redeclaration check. This was masked in the
test because each eval had an initializer, and the initializer was what
triggered the exception.

This patch tightens the test by removing initializers and fixes the bug in
DeclareLookupSlot.

Also change the test to use assertThrows where possible.

BUG=v8:4550
LOG=n

Review URL: https://codereview.chromium.org/1437003006

Cr-Commit-Position: refs/heads/master@{#31995}