Fix Pango font rendering with HiDPi displays on Linux.

chrome/browser/ui/libgtk2ui/gtk2_ui.h

Index: chrome/browser/ui/libgtk2ui/gtk2_ui.h
diff --git a/chrome/browser/ui/libgtk2ui/gtk2_ui.h b/chrome/browser/ui/libgtk2ui/gtk2_ui.h
index d936d89584d3cd42b7d0051e78b00f1247477d1e..d8af831c4771209b6a4230694027f27ce65ffc07 100644
--- a/chrome/browser/ui/libgtk2ui/gtk2_ui.h
+++ b/chrome/browser/ui/libgtk2ui/gtk2_ui.h
@@ -118,6 +118,9 @@ class Gtk2UI : public views::LinuxUI {
   bool MatchEvent(const ui::Event& event,
                   std::vector<ui::TextEditCommandAuraLinux>* commands) override;
 
+  // ui::Views::LinuxUI:
+  void UpdateDeviceScaleFactor(float device_scale_factor) override;
+
  private:
   typedef std::map<int, SkColor> ColorMap;
   typedef std::map<int, color_utils::HSL> TintMap;
@@ -262,6 +265,8 @@ class Gtk2UI : public views::LinuxUI {
   // instance.
   NativeThemeGetter native_theme_overrider_;
 
+  float device_scale_factor_;
+
   DISALLOW_COPY_AND_ASSIGN(Gtk2UI);
 };