gn: start of format command

tools/gn/format_test_data/012.gn

Index: tools/gn/format_test_data/012.gn
diff --git a/tools/gn/format_test_data/012.gn b/tools/gn/format_test_data/012.gn
new file mode 100644
index 0000000000000000000000000000000000000000..1da385c00e89efdba1183dad69573dc7586bcef1
--- /dev/null
+++ b/tools/gn/format_test_data/012.gn
@@ -0,0 +1,16 @@
+# (A sample top level block comment)
+# 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.
+
+if (is_win) {
+    # This is some special stuff for Windows
+    sources = ["win.cc"] } else if (is_linux) {
+
+    # This is a block comment inside the linux block, but not attached.
+
+    sources = ["linux.cc"]
+} else {
+  # A comment with trailing spaces            
+sources = ["wha.cc"] }
+