Implement StereoPannerNode for robust stereo panning

Source/platform/audio/Spatializer.cpp

Index: Source/platform/audio/Spatializer.cpp
diff --git a/Source/platform/audio/Spatializer.cpp b/Source/platform/audio/Spatializer.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..3f470bd1bde6e620554d1bd398617915eb9de8e3
--- /dev/null
+++ b/Source/platform/audio/Spatializer.cpp
@@ -0,0 +1,33 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#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;
+    default:
+        ASSERT_NOT_REACHED();
+        return nullptr;
+    }
+
+    return panner;
+}
+
+} // namespace blink
+
+#endif // ENABLE(WEB_AUDIO)