gclient flatten: handle GN settings

Bug: 570091
Change-Id: I5c7cf00722c47a2063a8635822c0bb270a26b524
Reviewed-on: https://chromium-review.googlesource.com/527632
Commit-Queue: Dirk Pranke <dpranke@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>

gclient.py

@@ -1698,6 +1698,9 @@ def CMDflatten(parser, args):
     return 1
 
   flattened_deps = '\n'.join(
+    _GNSettingsToLines(
+        client.dependencies[0]._gn_args_file,
+        client.dependencies[0]._gn_args) +
     _DepsToLines(deps) +
     _HooksToLines('hooks', hooks) +
     _HooksToLines('pre_deps_hooks', pre_deps_hooks) +
@@ -1802,6 +1805,16 @@ def _AddDep(dep, deps, unpinned_deps):
     unpinned_deps[dep.name] = dep
 
 
+def _GNSettingsToLines(gn_args_file, gn_args):
+  s = []
+  if gn_args_file:
+    s.extend([
+        'gclient_gn_args_file = "%s"' % gn_args_file,
+        'gclient_gn_args = %r' % gn_args,
+    ])
+  return s
+
+
 def _DepsToLines(deps):
   """Converts |deps| dict to list of lines for output."""
   s = ['deps = {']

testing_support/fake_repos.py

@@ -456,6 +456,11 @@ pre_deps_hooks = [
 
     self._commit_git('repo_6', {
       'DEPS': """
+vars = {
+  'DummyVariable': 'repo',
+}
+gclient_gn_args_file = 'src/gclient.args'
+gclient_gn_args = ['DummyVariable']
 deps = {
   'src/repo2': {
     'url': '%(git_base)srepo_2@%(hash)s',

tests/gclient_smoketest.py

@@ -570,6 +570,8 @@ class GClientSmokeGIT(GClientSmokeBase):
       deps_contents = f.read()
 
     self.assertEqual([
+        'gclient_gn_args_file = "src/gclient.args"',
+        'gclient_gn_args = [\'DummyVariable\']',
         'deps = {',
         '  # src -> src/repo2 -> foo/bar',
         '  "foo/bar": {',