Simplify handling of BiDi cursor movement

ui/base/range/range.h

 // Copyright (c) 2011 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.
 
 #ifndef UI_GFX_RANGE_H_
 #define UI_GFX_RANGE_H_
 
 #include <iosfwd>
 
 #include "base/basictypes.h"
@@ skipping 69 matching lines @@
   bool operator!=(const Range& other) const;
   bool EqualsIgnoringDirection(const Range& other) const;
 
   // Returns true if this range intersects the specified |range|.
   bool Intersects(const Range& range) const;
 
   // Returns true if this range contains the specified |range|.
   bool Contains(const Range& range) const;
 
   // Computes the intersection of this range with the given |range|.
-  // If they don't intersects, it returns an InvalidRange().
+  // If they don't intersect, it returns an InvalidRange().
+  // The returned range is always empty or forward (never reversed).
   Range Intersect(const Range& range) const;
 
 #if defined(OS_MACOSX)
   Range& operator=(const NSRange& range);
 
   // NSRange does not store the directionality of a range, so if this
   // is_reversed(), the range will get flipped when converted to an NSRange.
   NSRange ToNSRange() const;
 #elif defined(OS_WIN)
   CHARRANGE ToCHARRANGE() const;
 #endif
   // GTK+ has no concept of a range.
 
  private:
   size_t start_;
   size_t end_;
 };
 
 UI_EXPORT std::ostream& operator<<(std::ostream& out, const ui::Range& range);
 
 }  // namespace gfx
 
 #endif  // UI_GFX_RANGE_H_