[Merge to M59] Gtk3: Add background class to tooltips

chrome/browser/ui/libgtkui/native_theme_gtk3.cc

Index: chrome/browser/ui/libgtkui/native_theme_gtk3.cc
diff --git a/chrome/browser/ui/libgtkui/native_theme_gtk3.cc b/chrome/browser/ui/libgtkui/native_theme_gtk3.cc
index 0c83717e1f925912674dd82e2350d8668f8836e1..87f2e62f63e60027440d1c5d19c165b3a7d48353 100644
--- a/chrome/browser/ui/libgtkui/native_theme_gtk3.cc
+++ b/chrome/browser/ui/libgtkui/native_theme_gtk3.cc
@@ -37,6 +37,12 @@ std::string GetGtkSettingsStringProperty(GtkSettings* settings,
   return prop_value;
 }
 
+ScopedStyleContext GetTooltipContext() {
+  return AppendCssNodeToStyleContext(
+      nullptr, GtkVersionCheck(3, 20) ? "#tooltip.background"
+                                      : "GtkWindow#window.background.tooltip");
+}
+
 SkBitmap GetWidgetBitmap(const gfx::Size& size,
                          GtkStyleContext* context,
                          BackgroundRenderMode bg_mode,
@@ -243,9 +249,12 @@ SkColor SkColorFromColorId(ui::NativeTheme::ColorId color_id) {
 
     // Tooltips
     case ui::NativeTheme::kColorId_TooltipBackground:
-      return GetBgColor("GtkTooltip#tooltip");
-    case ui::NativeTheme::kColorId_TooltipText:
-      return GetFgColor("GtkTooltip#tooltip GtkLabel");
+      return GetBgColorFromStyleContext(GetTooltipContext());
+    case ui::NativeTheme::kColorId_TooltipText: {
+      auto context = GetTooltipContext();
+      context = AppendCssNodeToStyleContext(context, "GtkLabel");
+      return GetFgColorFromStyleContext(context);
+    }
 
     // Trees and Tables (implemented on GTK using the same class)
     case ui::NativeTheme::kColorId_TableBackground:
@@ -409,7 +418,6 @@ NativeThemeGtk3::NativeThemeGtk3() {
   g_type_class_unref(g_type_class_ref(gtk_separator_get_type()));
   g_type_class_unref(g_type_class_ref(gtk_spinner_get_type()));
   g_type_class_unref(g_type_class_ref(gtk_text_view_get_type()));
-  g_type_class_unref(g_type_class_ref(gtk_tooltip_get_type()));
   g_type_class_unref(g_type_class_ref(gtk_tree_view_get_type()));
   g_type_class_unref(g_type_class_ref(gtk_window_get_type()));