Add Protobuf support in cc for gfx objects

cc/proto/BUILD.gn

+# 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.
+
+import("//third_party/protobuf/proto_library.gni")
+
+group("proto") {

[danakj, 2015/10/19 17:24:30]

Can you leave a comment explaining to future-us why you used a group here? (Also
yay)

[David Trainor- moved to gerrit, 2015/10/19 18:50:38]

Done.

+  deps = [
+    ":cc_proto",
+  ]
+}
+
+component("cc_proto") {
+  visibility = [ ":proto" ]

[danakj, 2015/10/19 17:24:30]

I did a google search for gn visibility and got nothing. Lacking docs, could you
leave a comment about why this is here also?

[David Trainor- moved to gerrit, 2015/10/19 18:50:38]

Done.  Basically only exposes this target to the targets specified in visibility
(so only "proto" can see/depend on this).

+
+  public_deps = [
+    ":proto_internal",
+  ]
+}
+
+proto_library("proto_internal") {
+  visibility = [ ":cc_proto" ]
+
+  sources = [
+    # TODO(dtrainor): Move the ui/gfx related protos to ui/gfx/proto once it is
+    # possible to include protos from other directories/targets (see
+    # crbug.com/542423).
+    "point.proto",
+    "pointf.proto",
+    "rect.proto",
+    "rectf.proto",
+    "size.proto",
+    "sizef.proto",
+    "transform.proto",
+  ]
+
+  deps = [
+    "//third_party/protobuf:protobuf_lite",
+  ]
+
+  cc_generator_options = "dllexport_decl=CC_PROTO_EXPORT:"
+  cc_include = "cc/proto/cc_proto_export.h"
+
+  defines = [ "CC_PROTO_IMPLEMENTATION" ]
+
+  # Warn if clang creates exit destructors.
+  extra_configs = [ "//build/config/compiler:wexit_time_destructors" ]
+}