Teach the IDL compiler about TreatNullAs=EmptyString

Source/bindings/v8/V8StringResource.h

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 148 matching lines @@
 };
 
 template <typename StringType>
 StringType v8StringToWebCoreString(v8::Handle<v8::String>, ExternalMode);
 String int32ToWebCoreString(int value);
 
 // V8StringResource is an adapter class that converts V8 values to Strings
 // 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

 };
 
 template <V8StringResourceMode Mode = DefaultMode>
 class V8StringResource {
 public:
     V8StringResource(v8::Handle<v8::Value> object)
         : m_v8Object(object)
         , m_mode(Externalize)
         , m_string()
     {
@@ skipping 46 matching lines @@
     v8::Handle<v8::Value> m_v8Object;
     ExternalMode m_mode;
     String m_string;
 };
 
 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()) {
         setString(String());
         return true;
     }
     return prepareBase();
 }
 
 template<> inline bool V8StringResource<WithUndefinedOrNullCheck>::prepare()
 {
     if (m_v8Object.IsEmpty() || m_v8Object->IsNull() || m_v8Object->IsUndefined()) {
         setString(String());
         return true;
     }
     return prepareBase();
 }
 
 } // namespace WebCore
 
 #endif // V8StringResource_h