Reland try/catch destructuring with a fix for the MemorySanitizer failure:
initialization_pos needs to be initialized in the DeclarationDescriptor.

This is a one line fix to http://crrev.com/a316db995e6e4253664920652ed4e5a38b2caeba

BUG=v8:811
LOG=y

Review URL: https://codereview.chromium.org/1411323008

Cr-Commit-Position: refs/heads/master@{#31834}