Adding PreRole in blink side to expose HTML pre tag with correct MSAA+IA2.

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 391 matching lines @@
 
     if (node && node->hasTagName(mainTag))
         return MainRole;
 
     if (node && node->hasTagName(navTag))
         return NavigationRole;
 
     if (node && node->hasTagName(asideTag))
         return ComplementaryRole;
 
+    if (node && node->hasTagName(preTag))
+        return PreRole;
+
     if (node && node->hasTagName(sectionTag))
         return RegionRole;
 
     if (node && node->hasTagName(addressTag))
         return ContentInfoRole;
 
     if (node && node->hasTagName(dialogTag))
         return DialogRole;
 
     // The HTML element should not be exposed as an element. That's what the RenderView element does.
@@ skipping 1970 matching lines @@
         if (label && label->renderer()) {
             LayoutRect labelRect = axObjectCache()->getOrCreate(label)->elementRect();
             result.unite(labelRect);
         }
     }
 
     return result;
 }
 
 } // namespace blink