AudioParam.setValueCurveAtTime() should copy the curve data

setValueCurveAtTime() should copy the curve data so that modifications
of the original array don't change what setValueCurveAtTime would
produce.

See description of value parameter at http://webaudio.github.io/web-audio-api/#widl-AudioParam-setValueCurveAtTime-AudioParam-Float32Array-values-double-startTime-double-duration

BUG=582980
TEST=audioparam-setValueCurve-copy.html

Review-Url: https://codereview.chromium.org/2016563002
Cr-Commit-Position: refs/heads/master@{#397161}
4 files changed