Fix Views inline autocomplete with multi-char graphemes.

ui/gfx/render_text.h

 // Copyright (c) 2012 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_RENDER_TEXT_H_
 #define UI_GFX_RENDER_TEXT_H_
 
 #include <algorithm>
 #include <cstring>
 #include <string>
@@ skipping 360 matching lines @@
   int GetBaseline();
 
   void Draw(Canvas* canvas);
 
   // Draws a cursor at |position|.
   void DrawCursor(Canvas* canvas, const SelectionModel& position);
 
   // Gets the SelectionModel from a visual point in local coordinates.
   virtual SelectionModel FindCursorPosition(const Point& point) = 0;
 
-  // Return true if cursor can appear in front of the character at |position|,
-  // which means it is a grapheme boundary or the first character in the text.
-  virtual bool IsCursorablePosition(size_t position) = 0;
+  // Returns true if the position is a valid logical index into text(), and is
+  // also a valid grapheme boundary, which may be used as a cursor position.
+  virtual bool IsValidCursorIndex(size_t index) = 0;
+
+  // Returns true if the position is a valid logical index into text(). Indices
+  // amid multi-character graphemes are allowed here, unlike IsValidCursorIndex.
+  virtual bool IsValidLogicalIndex(size_t index);
 
   // Get the visual bounds of a cursor at |caret|. These bounds typically
   // represent a vertical line if |insert_mode| is true. Pass false for
   // |insert_mode| to retrieve the bounds of the associated glyph. These bounds
   // are in local coordinates, but may be outside the visible region if the text
   // is longer than the textfield. Subsequent text, cursor, or bounds changes
   // may invalidate returned values. Note that |caret| must be placed at
-  // grapheme boundary, that is, |IsCursorablePosition(caret.caret_pos())| must
-  // return true.
+  // grapheme boundary, i.e. caret.caret_pos() must be a cursorable position.
   Rect GetCursorBounds(const SelectionModel& caret, bool insert_mode);
 
   // Compute the current cursor bounds, panning the text to show the cursor in
   // the display rect if necessary. These bounds are in local coordinates.
   // Subsequent text, cursor, or bounds changes may invalidate returned values.
   const Rect& GetUpdatedCursorBounds();
 
   // Given an |index| in text(), return the next or previous grapheme boundary
-  // in logical order (that is, the nearest index for which
-  // |IsCursorablePosition(index)| returns true). The return value is in the
-  // range 0 to text().length() inclusive (the input is clamped if it is out of
-  // that range). Always moves by at least one character index unless the
+  // in logical order (i.e. the nearest cursorable index). The return value is
+  // in the range 0 to text().length() inclusive (the input is clamped if it is
+  // out of that range). Always moves by at least one character index unless the
   // supplied index is already at the boundary of the string.
   size_t IndexOfAdjacentGrapheme(size_t index,
                                  LogicalCursorDirection direction);
 
   // Return a SelectionModel with the cursor at the current selection's start.
   // The returned value represents a cursor/caret position without a selection.
   SelectionModel GetSelectionModelForSelectionStart();
 
   // Sets shadows to drawn with text.
   void SetTextShadows(const ShadowValues& shadows);
@@ skipping 291 matching lines @@
   // Lines computed by EnsureLayout. These should be invalidated with
   // ResetLayout and on |display_rect_| changes.
   std::vector<internal::Line> lines_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderText);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_RENDER_TEXT_H_