[AiS] for desktop, two lines and font sytles

ui/gfx/render_text.cc

 // 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.
 
 #include "ui/gfx/render_text.h"
 
 #include <algorithm>
 #include <climits>
 
 #include "base/command_line.h"
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 // static
 RenderText* RenderText::CreateInstanceForEditing() {
   return new RenderTextHarfBuzz;
 }
 
 void RenderText::SetText(const base::string16& text) {
   DCHECK(!composition_range_.IsValid());
   if (text_ == text)
     return;
-  text_ = text;
+  text_.clear();
+  AppendText(text);
 
-  // Adjust ranged styles, baselines, and colors to accommodate a new text
-  // length. Clear style ranges as they might break new text graphemes and apply
+  // Clear style ranges as they might break new text graphemes and apply
   // the first style to the whole text instead.
-  const size_t text_length = text_.length();
-  colors_.SetMax(text_length);
+  colors_.SetValue(colors_.breaks().begin()->second);
   baselines_.SetValue(baselines_.breaks().begin()->second);
-  baselines_.SetMax(text_length);
   for (size_t style = 0; style < NUM_TEXT_STYLES; ++style) {
     BreakList<bool>& break_list = styles_[style];
     break_list.SetValue(break_list.breaks().begin()->second);
-    break_list.SetMax(text_length);
   }
-  cached_bounds_and_offset_valid_ = false;
 
   // Reset selection model. SetText should always followed by SetSelectionModel
   // or SetCursorPosition in upper layer.
   SetSelectionModel(SelectionModel());
 
   // Invalidate the cached text direction if it depends on the text contents.
   if (directionality_mode_ == DIRECTIONALITY_FROM_TEXT)
     text_direction_ = base::i18n::UNKNOWN_DIRECTION;
+}
 
+void RenderText::AppendText(const base::string16& text) {
+  text_ += text;
+  // Adjust ranged styles and colors to accommodate a new text length.
+  const size_t text_length = text_.length();
+  colors_.SetMax(text_length);
+  baselines_.SetMax(text_length);
+  for (size_t style = 0; style < NUM_TEXT_STYLES; ++style) {
+    BreakList<bool>& break_list = styles_[style];
+    break_list.SetMax(text_length);
+  }
+  cached_bounds_and_offset_valid_ = false;
   obscured_reveal_index_ = -1;
   OnTextAttributeChanged();
 }
 
 void RenderText::SetHorizontalAlignment(HorizontalAlignment alignment) {
   if (horizontal_alignment_ != alignment) {
     horizontal_alignment_ = alignment;
     display_offset_ = Vector2d();
     cached_bounds_and_offset_valid_ = false;
   }
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   SetDisplayOffset(display_offset_.x() + delta_x);
 }
 
 void RenderText::DrawSelection(Canvas* canvas) {
   for (const Rect& s : GetSubstringBounds(selection()))
     canvas->FillRect(s, selection_background_focused_color_);
 }
 
 }  // namespace gfx