Implement StereoPannerNode for robust stereo panning

Source/modules/webaudio/AudioContext.cpp

Index: Source/modules/webaudio/AudioContext.cpp
diff --git a/Source/modules/webaudio/AudioContext.cpp b/Source/modules/webaudio/AudioContext.cpp
index e8b2c9cb721f98a30f28d4469e7b128eee224a4f..1e03ed25fe6479353de3df08fc0f94274bcb8901 100644
--- a/Source/modules/webaudio/AudioContext.cpp
+++ b/Source/modules/webaudio/AudioContext.cpp
@@ -60,6 +60,7 @@
 #include "modules/webaudio/PannerNode.h"
 #include "modules/webaudio/PeriodicWave.h"
 #include "modules/webaudio/ScriptProcessorNode.h"
+#include "modules/webaudio/StereoPannerNode.h"
 #include "modules/webaudio/WaveShaperNode.h"
 #include "platform/audio/FFTFrame.h"
 #include "platform/audio/HRTFPanner.h"
@@ -365,6 +366,12 @@ ScriptProcessorNode* AudioContext::createScriptProcessor(size_t bufferSize, size
     return node;
 }
 
+StereoPannerNode* AudioContext::createStereoPanner()
+{
+    ASSERT(isMainThread());
+    return StereoPannerNode::create(this, m_destinationNode->sampleRate());
+}
+
 BiquadFilterNode* AudioContext::createBiquadFilter()
 {
     ASSERT(isMainThread());