Bug 851949 - Avoid setting AudioParam values needlessly; r=roc

content/media/webaudio/AudioParam.h

@@ -64,6 +64,10 @@ public:
   // sure that the callback is called every time that this object gets mutated.
   void SetValue(float aValue)
   {
+    // Optimize away setting the same value on an AudioParam
+    if (HasSimpleValue() && fabsf(GetValue() - aValue) < 1e-7) {
+      return;
+    }
     AudioParamTimeline::SetValue(aValue);
     mCallback(mNode);
   }