Do not ignore the text style properties when checking styles in EditingStyle.

third_party/WebKit/Source/core/editing/EditingStyle.cpp

 /*
  * Copyright (C) 2007, 2008, 2009 Apple Computer, Inc.
  * Copyright (C) 2010, 2011 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 733 matching lines @@
 
     if (selection.isCaret())
         return triStateOfStyle(EditingStyle::styleAtSelectionStart(selection));
 
     TriState state = FalseTriState;
     bool nodeIsStart = true;
     for (Node& node : NodeTraversal::startsAt(selection.start().anchorNode())) {
         if (node.layoutObject() && node.hasEditableStyle()) {
             CSSComputedStyleDeclaration* nodeStyle = CSSComputedStyleDeclaration::create(&node);
             if (nodeStyle) {
-                TriState nodeState = triStateOfStyle(nodeStyle, node.isTextNode() ? EditingStyle::DoNotIgnoreTextOnlyProperties : EditingStyle::IgnoreTextOnlyProperties);
+                // Pass EditingStyle::DoNotIgnoreTextOnlyProperties without checking if node.isTextNode()
+                // because the node can be an element node. See bug http://crbug.com/584939.
+                TriState nodeState = triStateOfStyle(nodeStyle, EditingStyle::DoNotIgnoreTextOnlyProperties);
                 if (nodeIsStart) {
                     state = nodeState;
                     nodeIsStart = false;
                 } else if (state != nodeState && node.isTextNode()) {
                     state = MixedTriState;
                     break;
                 }
             }
         }
         if (&node == selection.end().anchorNode())
@@ skipping 963 matching lines @@
 {
     for (Node* ancestor = node; ancestor; ancestor = ancestor->parentNode()) {
         CSSComputedStyleDeclaration* ancestorStyle = CSSComputedStyleDeclaration::create(ancestor);
         if (!hasTransparentBackgroundColor(ancestorStyle))
             return ancestorStyle->getPropertyCSSValue(CSSPropertyBackgroundColor);
     }
     return nullptr;
 }
 
 } // namespace blink