[turbofan] Make throwing expressions kill the environment.

[turbofan] Make throwing expressions kill the environment.

This ensures that all expressions that throw actually mark the current
environment as dead in the AstGraphBuilder. This prevents live ranges
from being unnecessarily increased by paths that don't fall-through.
Note that we can do that because Runtime::kThrowFoo never returns.

R=svenpanne@chromium.org

Committed: https://crrev.com/e5ac65094cbda4f6345a0633d592c4cbe2c58446
Cr-Commit-Position: refs/heads/master@{#27546}

[Sven Panne, 2015-03-31 13:57:31]

lgtm

[Michael Starzinger, 2015-03-31 14:24:06]

The CQ bit was checked by mstarzinger@chromium.org

[commit-bot: I haz the power, 2015-03-31 14:24:24]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1049203002/20001

[commit-bot: I haz the power, 2015-03-31 14:26:01]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-03-31 14:26:09]

Patchset 2 (id:??) landed as
https://crrev.com/e5ac65094cbda4f6345a0633d592c4cbe2c58446
Cr-Commit-Position: refs/heads/master@{#27546}