Expose html placeholder attribute as AXPlaceholder: <value> on MAC.

ui/accessibility/ax_node_data.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/accessibility/ax_node_data.h"
 
 #include <set>
 
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
@@ skipping 261 matching lines @@
         break;
       case AX_ATTR_LIVE_STATUS:
         result += " live=" + value;
         break;
       case AX_ATTR_CONTAINER_LIVE_RELEVANT:
         result += " container_relevant=" + value;
         break;
       case AX_ATTR_CONTAINER_LIVE_STATUS:
         result += " container_live=" + value;
         break;
+      case AX_ATTR_PLACEHOLDER:
+        result += "placeholder" + value;
+        break;
       case AX_ATTR_ROLE:
         result += " role=" + value;
         break;
       case AX_ATTR_SHORTCUT:
         result += " shortcut=" + value;
         break;
      case AX_ATTR_TEXT_INPUT_TYPE:
         result += " text_input_type=" + value;
         break;
       case AX_ATTR_URL:
@@ skipping 115 matching lines @@
     }
   }
 
   if (!child_ids.empty())
     result += " child_ids=" + IntVectorToString(child_ids);
 
   return result;
 }
 
 }  // namespace ui