Use Position instead of VisiblePosition for SurroundingText.

Source/core/editing/SurroundingText.h

 /*
  * Copyright (C) 2012 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 18 matching lines @@
  */
 
 #ifndef SurroundingText_h
 #define SurroundingText_h
 
 #include "platform/heap/Handle.h"
 #include "wtf/text/WTFString.h"
 
 namespace WebCore {
 
+class Position;
 class Range;
-class VisiblePosition;
 
 class SurroundingText {
     WTF_MAKE_NONCOPYABLE(SurroundingText);
 public:
-    SurroundingText(const VisiblePosition&, unsigned maxLength);
+    SurroundingText(const Position&, unsigned maxLength);
 
     String content() const;
     unsigned positionOffsetInContent() const;
 
     PassRefPtrWillBeRawPtr<Range> rangeFromContentOffsets(unsigned startOffsetInContent, unsigned endOffsetInContent);
 
 private:
     RefPtrWillBePersistent<Range> m_contentRange;
     size_t m_positionOffsetInContent;
 };
 
 } // namespace WebCore
 
 #endif // SurroundingText_h