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

Source/modules/accessibility/AXNodeObject.cpp

 /*
 * Copyright (C) 2012, 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
@@ skipping 949 matching lines @@
 
     const AtomicString& ariaAutoComplete = getAttribute(aria_autocompleteAttr).lower();
 
     if (ariaAutoComplete == "inline" || ariaAutoComplete == "list"
         || ariaAutoComplete == "both")
         return ariaAutoComplete;
 
     return String();
 }
 
+String AXNodeObject::placeholder() const
+{
+    String placeholder;
+    if (node()) {
+        if (isHTMLInputElement(*node())) {
+            HTMLInputElement* inputElement = toHTMLInputElement(node());
+            placeholder = inputElement->strippedPlaceholder();
+        } else if (isHTMLTextAreaElement(*node())) {
+            HTMLTextAreaElement* textAreaElement = toHTMLTextAreaElement(node());
+            placeholder = textAreaElement->strippedPlaceholder();
+        }
+    }
+    return placeholder;
+}
+
 String AXNodeObject::text() const
 {
     // If this is a user defined static text, use the accessible name computation.
     if (ariaRoleAttribute() == StaticTextRole)
         return ariaAccessibilityDescription();
 
     if (!isTextControl())
         return String();
 
     Node* node = this->node();
@@ skipping 949 matching lines @@
     float range = maxValueForRange() - minValueForRange();
     float value = valueForRange();
 
     value += range * (percentChange / 100);
     setValue(String::number(value));
 
     axObjectCache()->postNotification(node(), AXObjectCacheImpl::AXValueChanged, true);
 }
 
 } // namespace blink