Adding MeterRole in blink to support MSAA+IA2 and AX roles for meter tag in Chromium.

Source/core/accessibility/AXRenderObject.cpp

 /*
 * Copyright (C) 2008 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:
 *
 * 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 364 matching lines @@
 
     if (isHTMLParagraphElement(node))
         return ParagraphRole;
 
     if (isHTMLLabelElement(node))
         return LabelRole;
 
     if (isHTMLDivElement(node))
         return DivRole;
 
+    if (isHTMLMeterElement(node))
+        return MeterRole;
+
     if (isHTMLFormElement(node))
         return FormRole;
 
     if (node && node->hasTagName(articleTag))
         return ArticleRole;
 
     if (node && node->hasTagName(mainTag))
         return MainRole;
 
     if (node && node->hasTagName(navTag))
@@ skipping 1979 matching lines @@
         if (label && label->renderer()) {
             LayoutRect labelRect = axObjectCache()->getOrCreate(label)->elementRect();
             result.unite(labelRect);
         }
     }
 
     return result;
 }
 
 } // namespace blink