Java: Implements union generation.

mojo/public/tools/bindings/generators/java_templates/interface_definition.tmpl

 {% from "constant_definition.tmpl" import constant_def %}
 {% from "enum_definition.tmpl" import enum_def %}
-{% from "struct_definition.tmpl" import struct_def %}
+{% from "data_types_definition.tmpl" import struct_def %}
 
 {%- macro declare_params(parameters, boxed=false) %}
 {%-   for param in parameters -%}
 {{param.kind|java_type(boxed)}} {{param|name}}
 {%- if not loop.last %}, {% endif %}
 {%-   endfor %}
 {%- endmacro %}
 
 {% macro declare_request_params(method) %}
 {{declare_params(method.parameters)}}
@@ skipping 263 matching lines @@
                                     {{flags_for_method(method, False)}},
                                     mRequestId));
             mMessageReceiver.accept(_message);
         }
     }
 {%   endif %}
 {% endfor %}
 
 }
 {% endmacro %}