Introducing new API placeHolder() to expose placeholder attribute on MAC

public/web/WebAXObject.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:
  *
  *     * 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 116 matching lines @@
     BLINK_EXPORT void colorValue(int& r, int& g, int& b) const;
     BLINK_EXPORT WebAXInvalidState invalidState() const;
     // Only used when invalidState() returns WebAXInvalidStateOther.
     BLINK_EXPORT WebString ariaInvalidValue() const;
     BLINK_EXPORT double estimatedLoadingProgress() const;
     BLINK_EXPORT WebString helpText() const;
     BLINK_EXPORT int headingLevel() const;
     BLINK_EXPORT int hierarchicalLevel() const;
     BLINK_EXPORT WebAXObject hitTest(const WebPoint&) const;
     BLINK_EXPORT WebString keyboardShortcut() const;
+    BLINK_EXPORT WebString placeholder() const;
     BLINK_EXPORT WebAXRole role() const;
     BLINK_EXPORT unsigned selectionEnd() const;
     BLINK_EXPORT unsigned selectionEndLineNumber() const;
     BLINK_EXPORT unsigned selectionStart() const;
     BLINK_EXPORT unsigned selectionStartLineNumber() const;
     BLINK_EXPORT WebString stringValue() const;
     BLINK_EXPORT WebString title() const;
     BLINK_EXPORT WebString language() const;
     BLINK_EXPORT WebAXObject titleUIElement() const;
     BLINK_EXPORT WebURL url() const;
@@ skipping 83 matching lines @@
     operator WTF::PassRefPtr<AXObject>() const;
 #endif
 
 private:
     WebPrivatePtr<AXObject> m_private;
 };
 
 } // namespace blink
 
 #endif