Teach the IDL compiler about TreatNullAs=EmptyString

Source/bindings/v8/V8StringResource.h

Index: Source/bindings/v8/V8StringResource.h
diff --git a/Source/bindings/v8/V8StringResource.h b/Source/bindings/v8/V8StringResource.h
index feb63a990952c79ad04828cd77fe693c67edb140..ddac5697e33881b82b56926545bc1e66ce3eb651 100644
--- a/Source/bindings/v8/V8StringResource.h
+++ b/Source/bindings/v8/V8StringResource.h
@@ -166,6 +166,7 @@ String int32ToWebCoreString(int value);
 // or AtomicStrings as appropriate, using multiple typecast operators.
 enum V8StringResourceMode {
     DefaultMode,
+    TreatNullAsEmptyString,
     WithNullCheck,
     WithUndefinedOrNullCheck

[haraken, 2014/01/15 11:57:36]

Shall we also rename WithNullCheck to TreatNullAsNullString, and
WithUndefinedOrNullCheck to TreatUndefinedOrNullAsNullString ?

[arv (Not doing code reviews), 2014/01/15 15:44:59]

sounds good to me

 };
@@ -234,6 +235,15 @@ template<> inline bool V8StringResource<DefaultMode>::prepare()
     return prepareBase();
 }
 
+template<> inline bool V8StringResource<TreatNullAsEmptyString>::prepare()
+{
+    if (m_v8Object.IsEmpty() || m_v8Object->IsNull()) {
+        setString(emptyString());
+        return true;
+    }
+    return prepareBase();
+}
+
 template<> inline bool V8StringResource<WithNullCheck>::prepare()
 {
     if (m_v8Object.IsEmpty() || m_v8Object->IsNull()) {