LibGtkUi: Partition NativeThemeGtk into NativeThemeGtk2 and NativeThemeGtk3

chrome/browser/ui/libgtkui/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 assert(is_linux, "This file should only be referenced on Linux")
 
 import("//build/config/features.gni")
 import("//build/config/linux/gtk/gtk.gni")
 import("//printing/features/features.gni")
 
@@ skipping 28 matching lines @@
   "gtk_key_bindings_handler.h",
   "gtk_status_icon.cc",
   "gtk_status_icon.h",
   "gtk_ui.cc",
   "gtk_ui.h",
   "gtk_util.cc",
   "gtk_util.h",
   "libgtkui_export.h",
   "menu_util.cc",
   "menu_util.h",
-  "native_theme_gtk.cc",
-  "native_theme_gtk.h",
   "print_dialog_gtk.cc",
   "print_dialog_gtk.h",
   "printing_gtk_util.cc",
   "printing_gtk_util.h",
   "select_file_dialog_impl.cc",
   "select_file_dialog_impl.h",
   "select_file_dialog_impl_gtk.cc",
   "select_file_dialog_impl_gtk.h",
   "select_file_dialog_impl_kde.cc",
   "skia_utils_gtk.cc",
@@ skipping 61 matching lines @@
       ":libgtk3ui",
     ]
   } else {
     public_deps = [
       ":libgtk2ui",
     ]
   }
 }
 
 component("libgtk2ui") {
-  sources = common_sources
+  sources = common_sources + [
+              "native_theme_gtk2.cc",
+              "native_theme_gtk2.h",
+            ]
   configs += common_configs
   defines = [ "LIBGTKUI_IMPLEMENTATION" ]
 
   # GTK2 pulls pangoft2 as dependency, and pangoft2 depends on harfbuzz.
   # To avoid missing indirectly referenced harfbuzz symbols from pango,
   # some hack is required when bundled harfbuzz is used and component build is
   # disabled.
   # See crbug.com/462689 for details.
   all_dependent_configs = [ "//third_party/harfbuzz-ng:pangoft2_link_hack" ]
 
   deps = common_deps + [
            "//build/config/linux/gtk2",
            "//build/config/linux/gtk2:gtkprint2",
          ]
   public_deps = [
     "//chrome/browser:theme_properties",
   ]
 }
 
 # This is compiled with "all" even when it's not referenced to ensure that
 # GTK3 continues to build. GTK3 is explicitly specified by some distros.
 component("libgtk3ui") {
-  sources = common_sources
+  sources = common_sources + [
+              "native_theme_gtk3.cc",
+              "native_theme_gtk3.h",
+            ]
   configs += common_configs
   defines = [ "LIBGTKUI_IMPLEMENTATION" ]
 
   deps = common_deps + [
            "//build/config/linux/gtk3",
            "//build/config/linux/gtk3:gtkprint3",
          ]
   public_deps = [
     "//chrome/browser:theme_properties",
   ]
 }