Write mojom and StructTraits for DisplaySnapshot.

ui/display/mojo/display_snapshot.typemap

Index: ui/display/mojo/display_snapshot.typemap
diff --git a/ui/display/mojo/display_snapshot.typemap b/ui/display/mojo/display_snapshot.typemap
new file mode 100644
index 0000000000000000000000000000000000000000..d291af773129c59f0da261a5e0af191213e80dae
--- /dev/null
+++ b/ui/display/mojo/display_snapshot.typemap
@@ -0,0 +1,14 @@
+# Copyright 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.
+
+mojom = "//ui/display/mojo/display_snapshot.mojom"
+public_headers = [ "//ui/display/types/display_snapshot.h" ]
+traits_headers = [ "//ui/display/mojo/display_snapshot_struct_traits.h" ]
+public_deps = [
+  "//ui/display",
+]
+deps = [
+  "//ui/gfx/geometry",
+]
+type_mappings = [ "display.mojom.DisplaySnapshot=std::unique_ptr<display::DisplaySnapshot>[move_only]" ]