This changes the IrOpcode::kThrow operator to have kNoThrow property,
which sounds unintuitive, but holds for our graphs. The operators is
used to indicate exceptional control flow out of the function, but in
itself does not throw, the throwing is done by a runtime call.

R=titzer@chromium.org
TEST=unittests/CommonOperatorTest/CommonSharedOperatorTest.Properties

Review URL: https://codereview.chromium.org/1046173002

Cr-Commit-Position: refs/heads/master@{#27541}