Make setTarget followed by linear or exponential ramp continuous.

When setTarget is followed by a linear or exponential ramp, the
current behavior produces discontinuous curves.  In this case, make
the curve continuous by inserting a setValue to freeze the curve at
the last value of the setTarget.  This establishes the starting point
for the following linear and exponential ramp to make it continuous.

WebAudio issue:
Spec proposal:


Cr-Commit-Position: refs/heads/master@{#391597}
3 files changed