Enable hidpi on Linux, refactor a bit on Windows to share

ui/gfx/pango_util.cc

Index: ui/gfx/pango_util.cc
diff --git a/ui/gfx/pango_util.cc b/ui/gfx/pango_util.cc
index a324b7b326c373323420c8a2cfeba7a9d11c1325..bdec8d49717cb6f08ce19e9b5c8866e2c067e7ec 100644
--- a/ui/gfx/pango_util.cc
+++ b/ui/gfx/pango_util.cc
@@ -28,6 +28,9 @@ namespace {
 // Marker for accelerators in the text.
 const gunichar kAcceleratorChar = '&';
 
+const double kStandardDPI = 96.0;
+const double kPointsPerInch = 72.0;
+
 // Creates and returns a PangoContext. The caller owns the context.
 PangoContext* GetPangoContext() {
   PangoFontMap* font_map = pango_cairo_font_map_get_default();
@@ -85,27 +88,6 @@ cairo_font_options_t* CreateCairoFontOptions(const FontRenderParams& params) {
   return cairo_font_options;
 }
 
-// Returns the DPI that should be used by Pango.
-double GetPangoDPI() {
-  static double dpi = -1.0;
-  if (dpi < 0.0) {
-    const gfx::LinuxFontDelegate* delegate = gfx::LinuxFontDelegate::instance();
-    if (delegate)
-      dpi = delegate->GetFontDPI();
-    if (dpi <= 0.0)
-      dpi = 96.0;
-  }
-  return dpi;
-}
-
-// Returns the number of pixels in a point.
-// - multiply a point size by this to get pixels ("device units")
-// - divide a pixel size by this to get points
-double GetPixelsInPoint() {
-  static double pixels_in_point = GetPangoDPI() / 72.0;  // 72 points in an inch
-  return pixels_in_point;
-}
-
 }  // namespace
 
 void SetUpPangoLayout(
@@ -163,7 +145,7 @@ void SetUpPangoLayout(
   // Set the layout's resolution to match the resolution used to convert from
   // points to pixels.
   pango_cairo_context_set_resolution(pango_layout_get_context(layout),
-                                     GetPangoDPI());
+                                     kStandardDPI);
 
   // Set text and accelerator character if needed.
   if (flags & Canvas::SHOW_PREFIX) {
@@ -205,9 +187,10 @@ int GetPangoFontSizeInPixels(PangoFontDescription* pango_font) {
   if (pango_font_description_get_size_is_absolute(pango_font))
     return pango_font_description_get_size(pango_font) / PANGO_SCALE;
 
+  const double scale = kStandardDPI / kPointsPerInch;
   // Otherwise, we need to convert from points.
-  return static_cast<int>(GetPixelsInPoint() *
-      pango_font_description_get_size(pango_font) / PANGO_SCALE + 0.5);
+  return static_cast<int>(
+      scale * pango_font_description_get_size(pango_font) / PANGO_SCALE + 0.5);
 }
 
 PangoFontMetrics* GetPangoFontMetrics(PangoFontDescription* desc) {