Get rid of last uses of deprecated toWebCoreString(v8::Handle<v8::Value>)

Source/bindings/v8/custom/V8PannerNodeCustom.cpp

Index: Source/bindings/v8/custom/V8PannerNodeCustom.cpp
diff --git a/Source/bindings/v8/custom/V8PannerNodeCustom.cpp b/Source/bindings/v8/custom/V8PannerNodeCustom.cpp
index 8b0d7c9490bd740a380103f15028a8e276b956e9..12d67466d257a7837a27bb92265f67a42071a44c 100644
--- a/Source/bindings/v8/custom/V8PannerNodeCustom.cpp
+++ b/Source/bindings/v8/custom/V8PannerNodeCustom.cpp
@@ -45,7 +45,7 @@ void V8PannerNode::panningModelAttributeSetterCustom(v8::Local<v8::Value> value,
     }
 
     if (value->IsString()) {
-        String model = toWebCoreString(value);
+        String model = toWebCoreString(value.As<v8::String>());
         if (model == "equalpower" || model == "HRTF" || model == "soundfield") {
             imp->setPanningModel(model);
             return;
@@ -69,7 +69,7 @@ void V8PannerNode::distanceModelAttributeSetterCustom(v8::Local<v8::Value> value
     }
 
     if (value->IsString()) {
-        String model = toWebCoreString(value);
+        String model = toWebCoreString(value.As<v8::String>());
         if (model == "linear" || model == "inverse" || model == "exponential") {
             imp->setDistanceModel(model);
             return;