Gtk3 ui: Add libgtk3ui as a separate build component

chrome/browser/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.
 
 import("//build/config/chrome_build.gni")
 import("//build/config/crypto.gni")
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//build/split_static_library.gni")
 import("//chrome/common/features.gni")
@@ skipping 2219 matching lines @@
 
   if (use_x11) {
     sources += [
       "chrome_browser_main_extra_parts_x11.cc",
       "chrome_browser_main_extra_parts_x11.h",
       "password_manager/password_store_x.cc",
       "password_manager/password_store_x.h",
     ]
   }
   if (use_aura && !use_ozone && is_desktop_linux) {
-    deps += [ "//chrome/browser/ui/libgtk2ui" ]
-    allow_circular_includes_from += [ "//chrome/browser/ui/libgtk2ui" ]
+    if (use_gtk3) {
+      deps += [ "//chrome/browser/ui/libgtk2ui:libgtk3ui" ]
+    } else {
+      deps += [ "//chrome/browser/ui/libgtk2ui:libgtk2ui" ]
+    }
   }
   if (is_posix && !is_mac) {
     sources += [
       "//chrome/app/chrome_crash_reporter_client.cc",
       "//chrome/app/chrome_crash_reporter_client.h",
     ]
     deps += [
       "//components/crash/content/app",
       "//components/crash/content/browser",
       "//components/version_info:generate_version_info",
@@ skipping 2077 matching lines @@
   # linking all of the test support.
   static_library("pepper_cdm_test_constants") {
     testonly = true
     visibility = [ "//chrome/*" ]
     sources = [
       "media/pepper_cdm_test_constants.cc",
       "media/pepper_cdm_test_constants.h",
     ]
   }
 }