Change defaults for build args to accommodate Flutter and Fuchsia.

build/flutter_args.gni

Index: build/flutter_args.gni
diff --git a/build/flutter_args.gni b/build/flutter_args.gni
new file mode 100644
index 0000000000000000000000000000000000000000..02399fd5561f34593f186f5e265e30a2316d8b2a
--- /dev/null
+++ b/build/flutter_args.gni
@@ -0,0 +1,7 @@
+# Copyright (c) 2017 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
+
+declare_args() {
+  is_flutter = false

[zra, 2017/08/07 22:11:13]

A comment above this line will display when someone runs the command, for
example 'gn args out/ReleaseX64 --list'

+}