Regenerate .mojo file if any dependent .dart sources change

mojo/public/tools/dart_snapshotter.py

Index: mojo/public/tools/dart_snapshotter.py
diff --git a/mojo/public/tools/dart_snapshotter.py b/mojo/public/tools/dart_snapshotter.py
index 5727fd01890df53377d49593cc1b9fd6a71e8118..5726d1fa71aabe27e9629459e8c478758e0b148f 100755
--- a/mojo/public/tools/dart_snapshotter.py
+++ b/mojo/public/tools/dart_snapshotter.py
@@ -14,6 +14,8 @@ def main():
   parser.add_argument('main', type=str)
   parser.add_argument('--package-root', type=str)
   parser.add_argument('--snapshot', type=str)
+  parser.add_argument('--depfile', type=str)
+  parser.add_argument('--build-output', type=str)
 
   args = parser.parse_args()
   if not os.path.isfile(args.executable):
@@ -23,6 +25,8 @@ def main():
     args.main,
     '--package-root=%s' % args.package_root,
     '--snapshot=%s' % args.snapshot,
+    '--depfile=%s' % args.depfile,
+    '--build-output=%s' % args.build_output,
   ])
 
 if __name__ == '__main__':