Updates subpixel positioning and hinting when DSF is changed

ui/gfx/font_render_params.h

Index: ui/gfx/font_render_params.h
diff --git a/ui/gfx/font_render_params.h b/ui/gfx/font_render_params.h
index 4ec8d3502f15a2981f179b9fb02547a942743e3a..977a4955c021fac22f9aa834964a9f3a851d208a 100644
--- a/ui/gfx/font_render_params.h
+++ b/ui/gfx/font_render_params.h
@@ -82,6 +82,9 @@ struct GFX_EXPORT FontRenderParamsQuery {
 
   // gfx::Font::FontStyle bit field, or -1 if unset.
   int style;
+
+  // The device scale factor of the display, or 0 if unset.
+  float device_scale_factor;
 };
 
 // Returns the appropriate parameters for rendering the font described by
@@ -99,6 +102,9 @@ GFX_EXPORT FontRenderParams GetFontRenderParams(
 GFX_EXPORT void ClearFontRenderParamsCacheForTest();
 
 #if defined(OS_CHROMEOS)
+// Gets the device scale factor to query the FontRenderParams.
+float GetFontRenderParamsDeviceScaleFactor();
+
 // Sets the device scale factor for FontRenderParams to decide
 // if it should enable subpixel positioning.
 GFX_EXPORT void SetFontRenderParamsDeviceScaleFactor(