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..fa8f9213111fadb5ceaaf44da554478abd053743 100644
--- a/LayoutTests/webaudio/audioparam-setValueCurveAtTime.html
+++ b/LayoutTests/webaudio/audioparam-setValueCurveAtTime.html
@@ -22,9 +22,10 @@ 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.)
-var maxAllowedError = 0;
+// 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 = 4.657e-10;
 
 // The amplitude of the sine wave.
 var sineAmplitude = 1;