Move the exception logic to the AudioNode creator

third_party/WebKit/Source/modules/webaudio/GainNode.cpp

Index: third_party/WebKit/Source/modules/webaudio/GainNode.cpp
diff --git a/third_party/WebKit/Source/modules/webaudio/GainNode.cpp b/third_party/WebKit/Source/modules/webaudio/GainNode.cpp
index 6c8ad44f22c19bbfa9e88346b24fbcc099cf33ab..bada5970788b44c481b88a1e4286507de4adf35f 100644
--- a/third_party/WebKit/Source/modules/webaudio/GainNode.cpp
+++ b/third_party/WebKit/Source/modules/webaudio/GainNode.cpp
@@ -114,16 +114,23 @@ void GainHandler::checkNumberOfChannelsForInput(AudioNodeInput* input)
 
 // ----------------------------------------------------------------
 
-GainNode::GainNode(AbstractAudioContext& context, float sampleRate)
+GainNode::GainNode(AbstractAudioContext& context)
     : AudioNode(context)
     , m_gain(AudioParam::create(context, ParamTypeGainGain, 1.0))
 {
-    setHandler(GainHandler::create(*this, sampleRate, m_gain->handler()));
+    setHandler(GainHandler::create(*this, context.sampleRate(), m_gain->handler()));
 }
 
-GainNode* GainNode::create(AbstractAudioContext& context, float sampleRate)
+GainNode* GainNode::create(AbstractAudioContext& context, ExceptionState& exceptionState)
 {
-    return new GainNode(context, sampleRate);
+    DCHECK(isMainThread());
+
+    if (context.isContextClosed()) {
+        context.throwExceptionForClosedState(exceptionState);
+        return nullptr;
+    }
+
+    return new GainNode(context);
 }
 
 AudioParam* GainNode::gain() const