Fix Pango font rendering with HiDPi displays on Linux.

ui/views/linux_ui/linux_ui.h

Index: ui/views/linux_ui/linux_ui.h
diff --git a/ui/views/linux_ui/linux_ui.h b/ui/views/linux_ui/linux_ui.h
index 3f3d22554b11f5aa4dd199b1289072f174c5ca46..088de922431d345fe354ba927850cb942e5bed42 100644
--- a/ui/views/linux_ui/linux_ui.h
+++ b/ui/views/linux_ui/linux_ui.h
@@ -150,6 +150,10 @@ class VIEWS_EXPORT LinuxUI : public ui::LinuxInputMethodContextFactory,
   // automatically. In case Chromium does not open a new window on startup,
   // e.g. an existing browser window already exists, this should be called.
   virtual void NotifyWindowManagerStartupComplete() = 0;
+
+  // Updates the device scale factor so that the default font size can be
+  // recalculated.
+  virtual void UpdateDeviceScaleFactor(float device_scale_factor) = 0;
 };
 
 }  // namespace views