Add a snapshot of flutter/engine/src/build to our sdk

build/config/ui.gni

+# 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.
+
+# This file contains UI-related build flags. It should theoretically be in the
+# src/ui directory and only things that depend on the ui module should get the
+# definitions.
+#
+# However, today we have many "bad" dependencies on some of these flags from,
+# e.g. base, so they need to be global.
+#
+# See also build/config/features.gni
+
+declare_args() {
+  # Indicates if Ash is enabled. Ash is the Aura Shell which provides a
+  # desktop-like environment for Aura. Requires use_aura = true
+  use_ash = is_win || is_linux
+
+  # Indicates if Ozone is enabled. Ozone is a low-level library layer for Linux
+  # that does not require X11.
+  use_ozone = false
+
+  # Indicates if GLFW is enabled. GLFW is an abstraction layer for the
+  # windowing system and OpenGL rendering, providing cross-platform support
+  # for creating windows and OpenGL surfaces and contexts, and handling
+  # window system events and input.
+  use_glfw = false
+
+  # Support ChromeOS touchpad gestures with ozone.
+  use_evdev_gestures = false
+
+  # Indicates if Aura is enabled. Aura is a low-level windowing library, sort
+  # of a replacement for GDI or GTK.
+  use_aura = is_win || is_linux
+
+  # True means the UI is built using the "views" framework.
+  toolkit_views = is_mac || is_win || is_chromeos || use_aura
+
+  # Whether the entire browser uses toolkit-views on Mac instead of Cocoa.
+  mac_views_browser = false
+
+  # Whether we should use glib, a low level C utility library.
+  use_glib = is_linux && !use_ozone
+}
+
+# Additional dependent variables -----------------------------------------------
+#
+# These variables depend on other variables and can't be set externally.
+
+use_cairo = false
+use_pango = false
+
+# Use GPU accelerated cross process image transport by default on linux builds
+# with the Aura window manager.
+ui_compositor_image_transport = use_aura && is_linux
+
+use_default_render_theme = use_aura || is_linux
+
+# Indicates if the UI toolkit depends on X11.
+use_x11 = is_linux && !use_ozone && !use_glfw
+
+use_ozone_evdev = use_ozone
+
+use_clipboard_aurax11 = is_linux && use_aura && use_x11
+
+enable_hidpi = is_mac || is_chromeos || is_win || is_linux
+
+enable_topchrome_md = false