Adding backgroundColor to WebCompositionUnderline and using it for InlineTextBox drawing.

Source/web/CompositionUnderlineBuilder.h

 /*
  * Copyright (C) 2010 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 27 matching lines @@
 
 namespace blink {
 
 // This class is used for converting from WebCompositionUnderline to
 // WebCore::CompositionUnderline.
 
 class CompositionUnderlineBuilder : public WebCore::CompositionUnderline {
 public:
     CompositionUnderlineBuilder(const WebCompositionUnderline& u)
         : WebCore::CompositionUnderline(u.startOffset, u.endOffset,
-                                        WebCore::Color(u.color), u.thick) { }
+            WebCore::Color(u.color), u.thick,
+            WebCore::Color(u.backgroundColor)) { }
 };
 
 } // namespace blink
 
 #endif