Detect missing glyphs as returned by Vista in RenderTextWin.

ui/gfx/render_text_win.h

Index: ui/gfx/render_text_win.h
===================================================================
--- ui/gfx/render_text_win.h	(revision 134923)
+++ ui/gfx/render_text_win.h	(working copy)
@@ -109,9 +109,15 @@
   // Given a |run|, returns the SelectionModel that contains the logical first
   // or last caret position inside (not at a boundary of) the run.
   // The returned value represents a cursor/caret position without a selection.
-  SelectionModel FirstSelectionModelInsideRun(internal::TextRun* run);
-  SelectionModel LastSelectionModelInsideRun(internal::TextRun* run);
+  SelectionModel FirstSelectionModelInsideRun(const internal::TextRun* run);
+  SelectionModel LastSelectionModelInsideRun(const internal::TextRun* run);
 
+  // Returns a range [start, end) over the run's text corresponding to the given
+  // glyph index. For example, if the glyph covers characters "fi" in a run with
+  // text "hifi", then the returned range will have |start| == 2 and |end| == 4.
+  ui::Range GetTextRangeForRunGlyph(const internal::TextRun* run,
+                                    size_t glyph_index) const;
+
   // Cached HDC for performing Uniscribe API calls.
   static HDC cached_hdc_;