Use org.gnome.desktop.interface text-scaling-factor directly

gtk-xft-dpi is updated based on this value, so using this directly makes more sense.

BUG=511580
TEST=manual.

Review URL: https://codereview.chromium.org/1242753005

Cr-Commit-Position: refs/heads/master@{#339957}

chrome/browser/ui/libgtk2ui/BUILD.gn

@@ -61,7 +61,14 @@ component("libgtk2ui") {
       "gconf_listener.h",
     ]
   }
-  defines = [ "LIBGTK2UI_IMPLEMENTATION" ]
+  defines = [
+    "LIBGTK2UI_IMPLEMENTATION",
+
+    # g_settings_list_schemas is deprecated, but this function is not
+    # available on earlier version that we still need to support.
+    # See build/config/linux/BUILD.gn:gio_config for details.
+    "GLIB_DISABLE_DEPRECATION_WARNINGS",
+  ]
 
   configs += [
     "//build/config/linux:gconf",

chrome/browser/ui/libgtk2ui/gtk2_ui.cc

@@ -9,6 +9,7 @@
 
 #include <pango/pango.h>
 #include <X11/Xlib.h>
+#include <gio/gio.h>
 
 #include "base/command_line.h"
 #include "base/debug/leak_annotations.h"
@@ -426,6 +427,21 @@ views::LinuxUI::NonClientMiddleClickAction GetDefaultMiddleClickAction() {
   }
 }
 
+double GetGnomeTextScalingFactor() {
+  const char kDesktopInterfaceSchema[] = "org.gnome.desktop.interface";
+  for (const gchar* const* schemas = g_settings_list_schemas(); *schemas;
+       schemas++) {
+    if (!strcmp(kDesktopInterfaceSchema, static_cast<const char*>(*schemas))) {
+      GSettings* settings = g_settings_new(kDesktopInterfaceSchema);
+      double scale = g_settings_get_double(settings, "text-scaling-factor");
+      g_object_unref(settings);
+      return scale;
+    }
+  }
+  // Fallback if the schema does not exist.
+  return GetFontDPI() / GetBaseDPI();
+}
+
 }  // namespace
 
 Gtk2UI::Gtk2UI()
@@ -1438,9 +1454,12 @@ void Gtk2UI::UpdateDeviceScaleFactor(float device_scale_factor) {
 float Gtk2UI::GetDeviceScaleFactor() const {
   if (gfx::Display::HasForceDeviceScaleFactor())
     return gfx::Display::GetForcedDeviceScaleFactor();
-  float scale = GetFontDPI() / GetBaseDPI();
-  // Round to 1 decimal, e.g. to 1.4.
-  return roundf(scale * 10) / 10;
+  // Linux chrome does not support dynamnic scale factor change. Use the
+  // value obtanied during startup. The value is rounded to 1 decimal, e.g.
+  // to 1.4, for safety.
+  static float device_scale_factor =
+      roundf(GetGnomeTextScalingFactor() * 10) / 10;
+  return device_scale_factor;
 }
 
 }  // namespace libgtk2ui

chrome/browser/ui/libgtk2ui/libgtk2ui.gyp

@@ -43,6 +43,10 @@
       ],
       'defines': [
         'LIBGTK2UI_IMPLEMENTATION',
+        # g_settings_list_schemas is deprecated, but this function is not
+        # available on earlier version that we still need to support.
+        # See build/linux/system.gyp:gio for details.
+        'GLIB_DISABLE_DEPRECATION_WARNINGS'
       ],
       # Several of our source files are named _gtk2.cc. This isn't to
       # differentiate them from their source files (ninja and make are sane

content/test/gpu/gpu_tests/pixel_expectations.py

@@ -11,4 +11,10 @@ class PixelExpectations(GpuTestExpectations):
     # Sample Usage:
     # self.Fail('Pixel.Canvas2DRedBox',
     #     ['mac', 'amd', ('nvidia', 0x1234)], bug=123)
+    self.Fail('Pixel.Canvas2DRedBox',
+               [ 'linux', ('nvidia', 0x104a)], bug=511580)
+    self.Fail('Pixel.CSS3DBlueBox',
+               [ 'linux', ('nvidia', 0x104a)], bug=511580)
+    self.Fail('Pixel.WebGLGreenTriangle',
+               [ 'linux', ('nvidia', 0x104a)], bug=511580)
     pass