This is a reland of e1cdda25
Original change's description:
> [turbofan] eagerly prune None types and deadness from the graph
> 
> In addition to using the {Dead} node to prune dead control nodes and nodes that 
> depend on them, we introduce a {DeadValue} node representing an impossible value 
> that can occur at any position in the graph. The extended {DeadCodeElimination}
> prunes {DeadValue} and its uses, inserting a crashing {Unreachable} node into
> the effect chain when possible. The remaining uses of {DeadValue} are handled
> in {EffectControlLinearizer}, where we always have access to the effect chain.
> In addition to explicitly introduced {DeadValue} nodes, we consider any value use
> of a node with type {None} as dead.
> 
> Bug: chromium:741225
> Change-Id: Icc4b636d1d018c452ba1a2fa7cd3e00e522f1655
> Reviewed-on: https://chromium-review.googlesource.com/641250
> Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
> Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#48208}

Bug: chromium:741225
Change-Id: I21316913dae02864f7a6d7c9269405a79f054138
Reviewed-on: https://chromium-review.googlesource.com/692034Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48232}