Compute the base dpi from X

X uses 96 as default, and alters the screen size
but it can be overwritten. Compute the dpi from X
to match what gtk sues as base.

Round the dsf to 1 decimals as finer grained value can cause rendering problem than benefit.

Gpu test expectation on nvidia needs to be updated, so mark these tests as failing now.

BUG=485183

Review URL: https://codereview.chromium.org/1136913005

Cr-Commit-Position: refs/heads/master@{#330212}

chrome/browser/ui/libgtk2ui/gtk2_ui.cc

@@ -8,6 +8,7 @@
 #include <set>
 
 #include <pango/pango.h>
+#include <X11/Xlib.h>
 
 #include "base/command_line.h"
 #include "base/debug/leak_annotations.h"
@@ -49,6 +50,7 @@
 #include "ui/gfx/image/image.h"
 #include "ui/gfx/skbitmap_operations.h"
 #include "ui/gfx/skia_util.h"
+#include "ui/gfx/x/x11_types.h"
 #include "ui/resources/grit/ui_resources.h"
 #include "ui/views/controls/button/label_button.h"
 #include "ui/views/controls/button/label_button_border.h"
@@ -378,20 +380,27 @@ gfx::FontRenderParams GetGtkFontRenderParams() {
   return params;
 }
 
-double GetDPI() {
+double GetBaseDPI() {
+  XDisplay* xdisplay = gfx::GetXDisplay();
+  int xscreen = DefaultScreen(xdisplay);
+  return (DisplayHeight(xdisplay, xscreen) * 25.4) /
+         DisplayHeightMM(xdisplay, xscreen);
+}
+
+double GetFontDPI() {
   GtkSettings* gtk_settings = gtk_settings_get_default();
   CHECK(gtk_settings);
   gint gtk_dpi = -1;
   g_object_get(gtk_settings, "gtk-xft-dpi", &gtk_dpi, NULL);
 
   // GTK multiplies the DPI by 1024 before storing it.
-  return (gtk_dpi > 0) ? gtk_dpi / 1024.0 : 96.0;
+  return (gtk_dpi > 0) ? gtk_dpi / 1024.0 : GetBaseDPI();
 }
 
 // Queries GTK for its font DPI setting and returns the number of pixels in a
 // point.
 double GetPixelsInPoint(float device_scale_factor) {
-  double dpi = GetDPI();
+  double dpi = GetFontDPI();
 
   // Take device_scale_factor into account — if Chrome already scales the
   // entire UI up by 2x, we should not also scale up.
@@ -1424,10 +1433,9 @@ void Gtk2UI::UpdateDeviceScaleFactor(float device_scale_factor) {
 }
 
 float Gtk2UI::GetDeviceScaleFactor() const {
-  const int kCSSDefaultDPI = 96;
-  float scale = GetDPI() / kCSSDefaultDPI;
-  // Round to 2 decimals, e.g. to 1.33.
-  return roundf(scale * 100) / 100;
+  float scale = GetFontDPI() / GetBaseDPI();
+  // Round to 1 decimal, e.g. to 1.4.
+  return roundf(scale * 10) / 10;
 }
 
 }  // namespace libgtk2ui

content/test/gpu/gpu_tests/pixel_expectations.py

@@ -11,4 +11,6 @@ class PixelExpectations(GpuTestExpectations):
     # Sample Usage:
     # self.Fail('Pixel.Canvas2DRedBox',
     #     ['mac', 'amd', ('nvidia', 0x1234)], bug=123)
-    pass
+    self.Fail('Pixel.Canvas2DRedBox', bug=485183)
+    self.Fail('Pixel.CSS3DBlueBox', bug=485183)
+    self.Fail('Pixel.WebGLGreenTriangle', bug=485183)

content/test/gpu/page_sets/pixel_tests.py

@@ -30,19 +30,19 @@ class PixelTestsPageSet(page_set_module.PageSet):
       url='file://../../data/gpu/pixel_canvas2d.html',
       name=base_name + '.Canvas2DRedBox',
       test_rect=[0, 0, 300, 300],
-      revision=4,
+      revision=5,
       page_set=self))
 
     self.AddUserStory(PixelTestsPage(
       url='file://../../data/gpu/pixel_css3d.html',
       name=base_name + '.CSS3DBlueBox',
       test_rect=[0, 0, 300, 300],
-      revision=12,
+      revision=13,
       page_set=self))
 
     self.AddUserStory(PixelTestsPage(
       url='file://../../data/gpu/pixel_webgl.html',
       name=base_name + '.WebGLGreenTriangle',
       test_rect=[0, 0, 300, 300],
-      revision=9,
+      revision=10,
       page_set=self))