Makes mojo generator generate export for constants

mojo/public/tools/bindings/generators/cpp_templates/module.h.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 variant -%}
 {%-   set variant_path = "%s-%s"|format(module.path, variant) -%}
 {%- else -%}
 {%-   set variant_path = module.path -%}
 {%- endif -%}
 
@@ skipping 79 matching lines @@
 
 {#--- Enums #}
 {%- if variant %}
 {%-   for enum in enums %}
 using {{enum.name}} = {{enum.name}};  // Alias for definition in the parent namespace.
 {%-   endfor %}
 {%- endif %}
 
 {#--- Constants #}
 {%- for constant in module.constants %}
-{{constant|format_constant_declaration}};
+{{constant|format_constant_declaration(export_attribute=export_attribute)}};
 {%- endfor %}
 
 {#--- Interface Forward Declarations -#}
 {%  for interface in interfaces %}
 class {{interface.name}};
 using {{interface.name}}Ptr = mojo::InterfacePtr<{{interface.name}}>;
 using {{interface.name}}PtrInfo = mojo::InterfacePtrInfo<{{interface.name}}>;
 using ThreadSafe{{interface.name}}Ptr =
     mojo::ThreadSafeInterfacePtr<{{interface.name}}>;
 using {{interface.name}}Request = mojo::InterfaceRequest<{{interface.name}}>;
@@ skipping 105 matching lines @@
 {#--- Union Serialization Helpers -#}
 {%  if unions %}
 {%-   for union in unions %}
 {%      include "union_traits_declaration.tmpl" %}
 {%-   endfor %}
 {%- endif %}
 
 }  // namespace mojo
 
 #endif  // {{header_guard}}