Mojo: Simplify typemap usage.

mojo/public/cpp/bindings/tests/struct_with_traits.typemap

Index: mojo/public/cpp/bindings/tests/struct_with_traits.typemap
diff --git a/mojo/public/cpp/bindings/tests/struct_with_traits.typemap b/mojo/public/cpp/bindings/tests/struct_with_traits.typemap
new file mode 100644
index 0000000000000000000000000000000000000000..cbaf7d482d0db6f439ff9b7b058555fcb757d770
--- /dev/null
+++ b/mojo/public/cpp/bindings/tests/struct_with_traits.typemap
@@ -0,0 +1,15 @@
+# Copyright 2015 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 = "//mojo/public/interfaces/bindings/tests/struct_with_traits.mojom"
+public_headers =
+    [ "//mojo/public/cpp/bindings/tests/struct_with_traits_impl.h" ]
+traits_headers =
+    [ "//mojo/public/cpp/bindings/tests/struct_with_traits_impl_traits.h" ]
+sources = [
+  "//mojo/public/cpp/bindings/tests/struct_with_traits_impl_traits.cc",

[yzshen1, 2016/04/05 17:36:14]

Is "struct_with_triats_impl.cc" missing?
Do we need to also specify deps that sources depend on?
I noticed that gpu_command_buffer.typemap specifies deps but not sources. I
wonder why is the difference.

A document explaining the design would help reviewers and future users to
understand.

[Sam McNally, 2016/04/06 07:02:53]

The typemap should have:
- deps for the native type
- public_headers containing the header of the native type
- traits_headers containing the header with the StructTraits for the native type
- sources containing the implementation of the StructTraits for the native type
- type_mappings

For native-only types, the typemap should have:
- deps for the native type and its ParamTraits
- public_headers containing the header of the native type
- traits_headers containing the header with the ParamTraits for the native type
- type_mappings

This was missing a dependency on a target containing StructWithTraitsImpl.
Yes.

[yzshen1, 2016/04/06 16:00:47]

Can |sources| in case #1 be compiled into one of the targets listed in |deps|
instead? That way case #1 and #2 seem more consistent.

[Sam McNally, 2016/04/07 00:19:43]

No, the sources in #1 depend on the generated mojom headers.

[yzshen1, 2016/04/08 19:58:25]

Of course. :) Thanks for explaining.

+]
+
+type_mappings =
+    [ "mojo.test.StructWithTraits=mojo::test::StructWithTraitsImpl" ]