Use interpolation for setValueCurveAtTime

LayoutTests/webaudio/audioparam-setValueCurveAtTime.html

Index: LayoutTests/webaudio/audioparam-setValueCurveAtTime.html
diff --git a/LayoutTests/webaudio/audioparam-setValueCurveAtTime.html b/LayoutTests/webaudio/audioparam-setValueCurveAtTime.html
index 137945f16a7c22a9c214c429d53e6f8d398e42ce..0d58222047a425759ce195206a4c0885ab058e47 100644
--- a/LayoutTests/webaudio/audioparam-setValueCurveAtTime.html
+++ b/LayoutTests/webaudio/audioparam-setValueCurveAtTime.html
@@ -22,8 +22,9 @@ description("Test AudioParam setValueCurveAtTime() functionality.");
 // Number of tests to run.
 var numberOfTests = 20;
 
-// Max allowed difference between the rendered data and the expected result.  (The error is zero
-// because the rendered curve should really be exactly the same as the reference.)
+// Max allowed difference between the rendered data and the expected result.  Because of the linear
+// interpolation, the rendered curve isn't exactly the same as the reference.  This value is
+// experimentally determined.
 var maxAllowedError = 0;
 
 // The amplitude of the sine wave.