Implement move by word, fix rendering of Arabic shape joining

ui/gfx/render_text_linux.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_RENDER_TEXT_LINUX_H_
 #define UI_GFX_RENDER_TEXT_LINUX_H_
 #pragma once
 
 #include <pango/pango.h>
 
@@ skipping 50 matching lines @@
   // The returned value represents a cursor/caret position without a selection.
   SelectionModel FirstSelectionModelInsideRun(const PangoItem* run) const;
   SelectionModel LastSelectionModelInsideRun(const PangoItem* run) const;
 
   // Get the selection model visually left or right of |current| by one
   // grapheme.
   // The returned value represents a cursor/caret position without a selection.
   SelectionModel LeftSelectionModel(const SelectionModel& current);
   SelectionModel RightSelectionModel(const SelectionModel& current);
 
+  // Get the selection model visually left or right of |current| by one word.
+  // The returned value represents a cursor/caret position without a selection.
+  SelectionModel LeftSelectionModelByWord(const SelectionModel& current);
+  SelectionModel RightSelectionModelByWord(const SelectionModel& current);
+
   // If |layout_| is NULL, create and setup |layout_|, retain and ref
   // |current_line_|. Return |layout_|.
   PangoLayout* EnsureLayout();
 
   // Unref |layout_| and |pango_line_|. Set them to NULL.
   void ResetLayout();
 
   // Setup pango attribute: foreground, background, font, strike.
   void SetupPangoAttributes(PangoLayout* layout);
 
@@ skipping 28 matching lines @@
   const char* layout_text_;
   // The text length.
   size_t layout_text_len_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderTextLinux);
 };
 
 }  // namespace gfx;
 
 #endif  // UI_GFX_RENDER_TEXT_LINUX_H_