Mojo C++ bindings: support enum validation.

mojo/public/tools/bindings/generators/cpp_templates/module-internal.h.tmpl

Index: mojo/public/tools/bindings/generators/cpp_templates/module-internal.h.tmpl
diff --git a/mojo/public/tools/bindings/generators/cpp_templates/module-internal.h.tmpl b/mojo/public/tools/bindings/generators/cpp_templates/module-internal.h.tmpl
index c59c9f75db9e1792a57606381f339581b59e6b4f..c761c253182af7d2b98ade6c76340697f70a08f3 100644
--- a/mojo/public/tools/bindings/generators/cpp_templates/module-internal.h.tmpl
+++ b/mojo/public/tools/bindings/generators/cpp_templates/module-internal.h.tmpl
@@ -63,6 +63,12 @@ class {{struct.name}}_Data;
 class {{union.name}}_Data;
 {%- endfor %}
 
+{#--- Enums #}
+{% from "enum_macros.tmpl" import enum_data_decl -%}
+{%- for enum in enums %}
+  {{enum_data_decl(enum)}}
+{%- endfor %}
+
 #pragma pack(push, 1)
 
 {#--- Unions must be declared first because they can be members of structs #}
@@ -71,11 +77,24 @@ class {{union.name}}_Data;
 {%    include "union_declaration.tmpl" %}
 {%- endfor %}
 
-{#--- Class declarations #}
+{#--- Struct class declarations #}
 {%  for struct in structs %}
 {%    include "struct_declaration.tmpl" %}
 {%- endfor %}
 
+{#--- Interface class declarations. They are needed only when they contain
+    enums. #}
+{%- for interface in interfaces %}
+{%-   if interface.enums %}
+class {{interface.name}}_Data {
+ public:
+{%-     for enum in interface.enums %}
+  {{enum_data_decl(enum)|indent(2)}}
+{%-     endfor %}
+};
+{%-   endif %}
+{%- endfor %}
+
 #pragma pack(pop)
 
 }  // namespace internal