Use pango underline metrics in RenderTextLinux.

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_
 #pragma once
 
 #include <algorithm>
 #include <cstring>
@@ skipping 30 matching lines @@
 
 // Internal helper class used by derived classes to draw text through Skia.
 class SkiaTextRenderer {
  public:
   explicit SkiaTextRenderer(Canvas* canvas);
   ~SkiaTextRenderer();
 
   void SetDrawLooper(SkDrawLooper* draw_looper);
   void SetFontSmoothingSettings(bool enable_smoothing, bool enable_lcd_text);
   void SetTypeface(SkTypeface* typeface);
-  void SetTextSize(int size);
+  void SetTextSize(SkScalar size);
   void SetFontFamilyWithStyle(const std::string& family, int font_style);
   void SetForegroundColor(SkColor foreground);
   void SetShader(SkShader* shader, const Rect& bounds);
+  void SetUnderlineMetrics(SkScalar thickness, SkScalar position);
   void DrawSelection(const std::vector<Rect>& selection, SkColor color);
   void DrawPosText(const SkPoint* pos,
                    const uint16* glyphs,
                    size_t glyph_count);
   void DrawDecorations(int x, int y, int width, const StyleRange& style);
 
  private:
   SkCanvas* canvas_skia_;
   bool started_drawing_;
   SkPaint paint_;
   SkRect bounds_;
   SkRefPtr<SkShader> deferred_fade_shader_;
+  SkScalar underline_thickness_;
+  SkScalar underline_position_;
 
   DISALLOW_COPY_AND_ASSIGN(SkiaTextRenderer);
 };
 
 }  // namespace internal
 
 // A visual style applicable to a range of text.
 struct UI_EXPORT StyleRange {
   StyleRange();
 
@@ skipping 407 matching lines @@
 
   // Text shadows to be drawn.
   ShadowValues text_shadows_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderText);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_RENDER_TEXT_H_