Add 'depfile' option to actions.

test/actions-depfile/depfile.gyp

Index: test/actions-depfile/depfile.gyp
diff --git a/test/actions-depfile/depfile.gyp b/test/actions-depfile/depfile.gyp
new file mode 100644
index 0000000000000000000000000000000000000000..dc2397de0544c7499e99c2dd8586e4d2c12c83d6
--- /dev/null
+++ b/test/actions-depfile/depfile.gyp
@@ -0,0 +1,25 @@
+# Copyright (c) 2015 Google Inc. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+{
+  'targets': [
+    {
+      'target_name': 'depfile_target',
+      'type': 'none',
+      'actions': [
+        {
+          'action_name': 'depfile_action',
+          'inputs': [
+            'input.txt',
+          ],
+          'outputs': [
+            'output.txt',
+          ],
+          'depfile': 'depfile.d',
+          'action': [ ]
+        },
+      ],
+    },
+  ],
+}