Version 3.31.25 (based on 4d71e0f413f19d4f0d6716bbd81cf68c2cc7b761 )

Stage ES6 block scoping (issue 2198).

Introduce legacy const slots in correct context (Chromium issue 410030).

Performance and stability improvements on all platforms.

Cr-Commit-Position: refs/heads/candidates@{#25299}