IDL: Add support for [TreatNullAs=EmptyString]

Source/bindings/core/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 144 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,
-    WithNullCheck,
-    WithUndefinedOrNullCheck
+    TreatNullAsEmptyString,
+    TreatNullAsNullString,
+    TreatNullAndUndefinedAsNullString
 };
 
 template <V8StringResourceMode Mode = DefaultMode>
 class V8StringResource {
 public:
     V8StringResource()
         : m_mode(Externalize)
     {
     }
 
@@ skipping 17 matching lines @@
     {
         setString(String());
     }
 
     bool prepare()
     {
         if (m_v8Object.IsEmpty())
             return true;
 
         if (!isValid()) {
-            setString(String());
+            setString(fallbackString());
             return true;
         }
 
         if (LIKELY(m_v8Object->IsString()))
             return true;
 
         if (LIKELY(m_v8Object->IsInt32())) {
             setString(int32ToWebCoreString(m_v8Object->Int32Value()));
             return true;
         }
 
         m_mode = DoNotExternalize;
         v8::TryCatch block;
         m_v8Object = m_v8Object->ToString();
         // Handle the case where an exception is thrown as part of invoking toString on the object.
         if (block.HasCaught()) {
             block.ReThrow();
             return false;
         }
         return true;
     }
     operator String() const { return toString<String>(); }
     operator AtomicString() const { return toString<AtomicString>(); }
 
 private:
     bool isValid() const;
+    String fallbackString() const;
 
     void setString(const String& string)
     {
         m_string = string;
         m_v8Object.Clear(); // To signal that String is ready.
     }
 
     template <class StringType>
     StringType toString() const
     {
         if (LIKELY(!m_v8Object.IsEmpty()))
             return v8StringToWebCoreString<StringType>(const_cast<v8::Handle<v8::Value>*>(&m_v8Object)->As<v8::String>(), m_mode);
 
         return StringType(m_string);
     }
 
     v8::Handle<v8::Value> m_v8Object;
     ExternalMode m_mode;
     String m_string;
 };
 
 template<> inline bool V8StringResource<DefaultMode>::isValid() const
 {
     return true;
 }
 
-template<> inline bool V8StringResource<WithNullCheck>::isValid() const
+template<> inline String V8StringResource<DefaultMode>::fallbackString() const
+{
+    ASSERT_NOT_REACHED();
+    return String();
+}
+
+template<> inline bool V8StringResource<TreatNullAsEmptyString>::isValid() const
 {
     return !m_v8Object->IsNull();
 }
 
-template<> inline bool V8StringResource<WithUndefinedOrNullCheck>::isValid() const
+template<> inline String V8StringResource<TreatNullAsEmptyString>::fallbackString() const
+{
+    return emptyString();
+}
+
+template<> inline bool V8StringResource<TreatNullAsNullString>::isValid() const
+{
+    return !m_v8Object->IsNull();
+}
+
+template<> inline String V8StringResource<TreatNullAsNullString>::fallbackString() const
+{
+    return String();
+}
+
+template<> inline bool V8StringResource<TreatNullAndUndefinedAsNullString>::isValid() const
 {
     return !m_v8Object->IsNull() && !m_v8Object->IsUndefined();
 }
 
+template<> inline String V8StringResource<TreatNullAndUndefinedAsNullString>::fallbackString() const
+{
+    return String();
+}
+
 } // namespace WebCore
 
 #endif // V8StringResource_h