Replace narrowPrecisionToFloat with clampTo<float>

All narrowPrecisionToFloat does is call clampTo<float>, so lets just
make the callers do that. We use clampTo directly all over so there's no
reason to hide it.

BUG=642096
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2

Review-Url: https://codereview.chromium.org/2342913003
Cr-Commit-Position: refs/heads/master@{#419086}
26 files changed