By now lazy allocation of block scopes probably doesn't make that much sense anymore, since the memory overhead significantly reduced. Not indirecting scope() over ScopeState is faster, which is more important at this point.

BUG=v8:5209

Change-Id: I2968f01252769e7b1198a0a0876765a06ab0d3bd
Reviewed-on: https://chromium-review.googlesource.com/445025Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Marja Hölttä <marja@chromium.org>
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#43313}