Add glad library for glfw.

DEPS

@@ -424,6 +424,9 @@ deps = {
   'src/third_party/pkg/when':
    Var('dart_git') + '/when.git' + '@' + '0.2.0',
 
+  'src/flutter/third_party/glad/scripts':
+   Var('github_git') + '/Dav1dde/glad.git' + '@' + 'de6c39e3040c987323b8ed078c36442f4fb681b3',
+
    'src/third_party/android_tools/ndk': {
      'packages': [
        {

third_party/glad/BUILD.gn

@@ -0,0 +1,72 @@
+# Copyright 2013 The Flutter Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+_glad_gen_dir = "$root_out_dir/gen/flutter/third_party/glad"
+_public_headers = [
+  "$_glad_gen_dir/include/KHR/khrplatform.h",
+  "$_glad_gen_dir/include/glad/glad.h",
+]
+_glad_sources = [ "$_glad_gen_dir/src/glad.c" ]
+
+config("glad_public") {
+  include_dirs = [ "$_glad_gen_dir/include" ]
+}
+
+source_set("glad") {
+  public_configs = [ ":glad_public" ]
+
+  public = _public_headers
+
+  sources = _glad_sources
+
+  deps = [
+    ":gen_glad_sources",
+  ]
+}
+
+action("gen_glad_sources") {
+  visibility = [ ":*" ]
+  script = "generate.py"
+  inputs = [
+    "scripts/glad/__init__.py",
+    "scripts/glad/__main__.py",
+    "scripts/glad/opener.py",
+    "scripts/glad/parse.py",
+    "scripts/glad/spec.py",
+    "scripts/glad/util.py",
+    "scripts/glad/files/__init__.py",
+    "scripts/glad/files/egl.xml",
+    "scripts/glad/files/glx.xml",
+    "scripts/glad/files/wgl.xml",
+    "scripts/glad/files/gl.xml",
+    "scripts/glad/files/khrplatform.h",
+    "scripts/glad/lang/__init__.py",
+    "scripts/glad/lang/common/__init__.py",
+    "scripts/glad/lang/common/generator.py",
+    "scripts/glad/lang/common/loader.py",
+    "scripts/glad/lang/common/util.py",
+    "scripts/glad/lang/c/__init__.py",
+    "scripts/glad/lang/c/debug.py",
+    "scripts/glad/lang/c/generator.py",
+    "scripts/glad/lang/c/loader/__init__.py",
+    "scripts/glad/lang/c/loader/gl.py",
+    "scripts/glad/lang/c/loader/wgl.py",
+    "scripts/glad/lang/c/loader/egl.py",
+    "scripts/glad/lang/c/loader/glx.py",
+  ]
+
+  outputs = _public_headers + _glad_sources
+
+  args = [
+    "--profile=compatibility",
+    "--api=gl=3.3",
+    "--generator=c",
+    "--spec=gl",
+    "--extensions=",
+    "--reproducible",
+    "--quiet",
+    "--out-path",
+    rebase_path("$_glad_gen_dir"),
+  ]
+}

third_party/glad/LICENSE

@@ -0,0 +1,25 @@
+Copyright 2013 The Flutter Authors. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without modification,
+are permitted provided that the following conditions are met:
+
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+    * Redistributions in binary form must reproduce the above
+      copyright notice, this list of conditions and the following
+      disclaimer in the documentation and/or other materials provided
+      with the distribution.
+    * Neither the name of Google Inc. nor the names of its
+      contributors may be used to endorse or promote products derived
+      from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
+ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

third_party/glad/generate.py

@@ -0,0 +1,13 @@
+#!/usr/bin/python
+# -*- coding: UTF-8 -*-
+
+# GN can't run python scripts in `python -m scripts/glad` mode,
+# so the generate.py file seems to be necessary.
+
+import os
+import sys
+sys.path.append(os.path.split(os.path.abspath(__file__))[0] + '/scripts')
+from glad import __main__
+
+if __name__ == '__main__':
+    __main__.main()