Remove custom code for JavaScriptCallFrame.setVariableValue() operation

Source/core/inspector/JavaScriptCallFrame.idl

Index: Source/core/inspector/JavaScriptCallFrame.idl
diff --git a/Source/core/inspector/JavaScriptCallFrame.idl b/Source/core/inspector/JavaScriptCallFrame.idl
index 1da3f094cb5494cbaa7751d234d66eeaad830589..7ce86e6fb8d7b33650b4ac318e9794052e5f57f7 100644
--- a/Source/core/inspector/JavaScriptCallFrame.idl
+++ b/Source/core/inspector/JavaScriptCallFrame.idl
@@ -39,7 +39,7 @@
     [Custom] any restart();
 
     // Only declarative scope (local, with and catch) is accepted. Returns undefined.
-    [Custom] any setVariableValue(long scopeIndex, DOMString variableName, any newValue);
+    any setVariableValue([Default=Undefined] optional long scopeIndex, [TreatNullAs=NullString, TreatUndefinedAs=NullString, Default=Undefined] optional DOMString variableName, [Default=Undefined] optional any newValue);
 
     readonly attribute JavaScriptCallFrame caller;
     readonly attribute long sourceID;