Make sure getAttribute() / setAttribute() callers use AtomicStrings

Source/core/html/forms/BaseButtonInputType.cpp

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  * Copyright (C) 2011 Apple 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.
@@ skipping 58 matching lines @@
     return new RenderButton(&element());
 }
 
 bool BaseButtonInputType::storesValueSeparateFromAttribute()
 {
     return false;
 }
 
 void BaseButtonInputType::setValue(const String& sanitizedValue, bool, TextFieldEventBehavior)
 {
-    element().setAttribute(valueAttr, sanitizedValue);
+    element().setAttribute(valueAttr, AtomicString(sanitizedValue));
 }
 
 } // namespace WebCore