Mojo: Add support for constants to the IDL compiler.

mojo/public/tools/bindings/generators/cpp_templates/module.cc.tmpl

 // Copyright 2013 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.
 
 #if defined(__clang__)
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wunused-private-field"
 #endif
 
 #include "{{module.path}}.h"
 
 #include "mojo/public/cpp/bindings/lib/bindings_serialization.h"
 #include "mojo/public/cpp/bindings/lib/message_builder.h"
 
 {%- for namespace in namespaces_as_array %}
 namespace {{namespace}} {
 {%- endfor %}
+
+{#--- Constants #}
+{%  for constant in module.constants %}
+const {{constant.kind|cpp_pod_type}} {{constant.name}} = {{constant.value|expression_to_text(module)}};
+{%- endfor %}
+
 namespace internal {
 namespace {
 
 #pragma pack(push, 1)
 
 {#--- Interface parameter definitions #}
 {%- for interface in interfaces %}
 {%-   for method in interface.methods %}
 {%-     set method_name = "k%s_%s_Name"|format(interface.name, method.name) %}
 const uint32_t {{method_name}} = {{method.ordinal}};
@@ skipping 15 matching lines @@
 {%-   include "struct_destructor.tmpl" %}
 {%- endfor %}
 
 {#--- Struct definitions #}
 {%  for struct in structs %}
 {%-   include "struct_definition.tmpl" %}
 {%- endfor %}
 
 }  // namespace internal
 
+{#--- Struct Constants #}
+{%- for struct in structs %}
+{%     for constant in struct.constants %}
+const {{constant.kind|cpp_pod_type}} {{struct.name}}::{{constant.name}} = {{constant.value|expression_to_text(module)}};
+{%-   endfor %}
+{%- endfor %}
+
 {#--- Struct builder definitions #}
 {%- for struct in structs %}
 {%-   include "struct_builder_definition.tmpl" %}
 {%- endfor %}
 
 {#--- Interface definitions #}
 {%- for interface in interfaces %}
 {%-   include "interface_definition.tmpl" %}
 {%- endfor %}
 {%- for namespace in namespaces_as_array|reverse %}
 }  // namespace {{namespace}}
 {%- endfor %}
 
 #if defined(__clang__)
 #pragma clang diagnostic pop
 #endif