Check if ArrayBuffer allocation in ArrayBufferBuilder is successful.

Source/wtf/ArrayBufferBuilder.h

 /*
  * Copyright (C) 2013 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 20 matching lines @@
 #ifndef ArrayBufferBuilder_h
 #define ArrayBufferBuilder_h
 
 #include "wtf/ArrayBuffer.h"
 #include "wtf/Noncopyable.h"
 #include "wtf/RefPtr.h"
 #include "wtf/text/WTFString.h"
 
 namespace WTF {
 
-// A utility class to build an ArrayBuffer instance.
+// A utility class to build an ArrayBuffer instance. Validity must be checked
+// by isValid() before using an instance.
 class WTF_EXPORT ArrayBufferBuilder {
     // Disallow copying since it's expensive and we don't want code to do it by
     // accident.
     WTF_MAKE_NONCOPYABLE(ArrayBufferBuilder);
 
 public:
     // Creates an ArrayBufferBuilder using the default capacity.
     ArrayBufferBuilder();
 
     ArrayBufferBuilder(unsigned capacity)
         : m_bytesUsed(0)
         , m_variableCapacity(true)
     {
         m_buffer = ArrayBuffer::create(capacity, 1);
     }
 
+    bool isValid() const
+    {
+        return m_buffer;
+    }
+
+    // Appending empty data is not allowed.
     unsigned append(const char* data, unsigned length);
 
     // Returns the accumulated data as an ArrayBuffer instance. If needed,
     // creates a new ArrayBuffer instance and copies contents from the internal
     // buffer to it. Otherwise, returns a PassRefPtr pointing to the internal
     // buffer.
     PassRefPtr<ArrayBuffer> toArrayBuffer();
 
     // Converts the accumulated data into a String using the default encoding.
     String toString();
@@ skipping 33 matching lines @@
     unsigned m_bytesUsed;
     bool m_variableCapacity;
     RefPtr<ArrayBuffer> m_buffer;
 };
 
 } // namespace WTF
 
 using WTF::ArrayBufferBuilder;
 
 #endif // ArrayBufferBuilder_h