Introduce firstRangeOf() as replacement of VisibleSelection::firstRange()

Source/core/editing/FrameSelection.cpp

 /*
  * Copyright (C) 2004, 2008, 2009, 2010 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 1482 matching lines @@
     VisibleSelection newSelection(range.startPosition(), range.endPosition(), affinity, directional == Directional);
     setSelection(newSelection, options);
     startObservingVisibleSelectionChange();
     return true;
 }
 
 PassRefPtrWillBeRawPtr<Range> FrameSelection::firstRange() const
 {
     if (m_logicalRange)
         return m_logicalRange->cloneRange();
-    return m_selection.firstRange();
+    return firstRangeOf(m_selection);
 }
 
 bool FrameSelection::isInPasswordField() const
 {
     HTMLTextFormControlElement* textControl = enclosingTextFormControl(start());
     return isHTMLInputElement(textControl) && toHTMLInputElement(textControl)->type() == InputTypeNames::password;
 }
 
 void FrameSelection::notifyAccessibilityForSelectionChange()
 {
@@ skipping 544 matching lines @@
 
 void showTree(const blink::FrameSelection* sel)
 {
     if (sel)
         sel->showTreeForThis();
     else
         fprintf(stderr, "Cannot showTree for (nil) FrameSelection.\n");
 }
 
 #endif