Improve RenderTextWin font fallback.

ui/gfx/render_text_linux.cc

 // 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.
 
 #include "ui/gfx/render_text_linux.h"
 
 #include <pango/pangocairo.h>
 #include <algorithm>
 
 #include "base/i18n/break_iterator.h"
@@ skipping 266 matching lines @@
   // Vertically centered.
   int text_y = offset.y() + ((bounds.height() - text_height) / 2);
   // TODO(xji): need to use SkCanvas->drawPosText() for gpu acceleration.
   cairo_move_to(cr, offset.x(), text_y);
   pango_cairo_show_layout(cr, layout_);
 
   cairo_restore(cr);
 }
 
 size_t RenderTextLinux::IndexOfAdjacentGrapheme(size_t index, bool next) {
+  if (index > text().length())
+    return text().length();
   EnsureLayout();
   return Utf16IndexOfAdjacentGrapheme(Utf16IndexToUtf8Index(index), next);
 }
 
 GSList* RenderTextLinux::GetRunContainingPosition(size_t position) const {
   GSList* run = current_line_->runs;
   while (run) {
     PangoItem* item = reinterpret_cast<PangoLayoutRun*>(run->data)->item;
     size_t run_start = Utf8IndexToUtf16Index(item->offset);
     size_t run_end = Utf8IndexToUtf16Index(item->offset + item->length);
@@ skipping 386 matching lines @@
 }
 
 void RenderTextLinux::GetSelectionBounds(std::vector<Rect>* bounds) {
   if (selection_visual_bounds_.empty())
     CalculateSubstringBounds(GetSelectionStart(), GetCursorPosition(),
                              &selection_visual_bounds_);
   *bounds = selection_visual_bounds_;
 }
 
 }  // namespace gfx