We cannot optimize away ToNumber conversions based on the Type that we
see in Crankshaft, as this might be the (unchecked or even pretruncated)
lower bound. We can only use the HType, which is based on the definition.

R=jkummerow@chromium.org
BUG=chromium:590989
LOG=n

Review URL: https://codereview.chromium.org/1757013002

Cr-Commit-Position: refs/heads/master@{#34445}