DeadValue was a constant node of type None. This is unsound in the
presence of re-scheduling. This CL adds a value input to DeadValue,
which preserves the dependency on the original node of type None.

This reland addresses the bug that the EffectControlLinearizer could destroy dependencies of DeadValue by attaching DeadValue nodes to the effect chain in the EffectControlLinearizer.

Bug: chromium:796041 chromium:798938
Change-Id: If47b54a7986d257eb63b437f855769b503679ff5
Reviewed-on: https://chromium-review.googlesource.com/850392Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50360}