Implement StereoPannerNode for robust stereo panning

Source/platform/audio/Spatializer.cpp

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+
+#include "config.h"
+
+#if ENABLE(WEB_AUDIO)
+
+#include "platform/audio/Spatializer.h"
+
+#include "platform/audio/StereoPanner.h"
+
+namespace blink {
+
+Spatializer* Spatializer::create(PanningModel model, float sampleRate)
+{
+    Spatializer* panner;
+
+    switch (model) {
+    case PanningModelEqualPower:
+        panner = new StereoPanner(sampleRate);
+        break;
+
+    // TODO: add the instantiation of BinauralPanner here.
+    // TODO: add the instantiation of SurroundPanner here.
+
+    default:
+        ASSERT_NOT_REACHED();
+        return nullptr;
+    }
+
+    return panner;
+}
+
+} // namespace blink
+
+#endif // ENABLE(WEB_AUDIO)