Add JS bindings validation logic for non-nullable types

mojo/public/tools/bindings/generators/js_templates/struct_definition.tmpl

 {#--- Begin #}
   function {{struct.name}}() {
     this.initDefaults_();
   }
 
 {#--- Enums #}
 {%- from "enum_definition.tmpl" import enum_def %}
 {%  for enum in struct.enums %}
   {{enum_def("%s.%s"|format(struct.name, enum.name), enum, module)}}
 {%  endfor %}
@@ skipping 15 matching lines @@
   {{struct.name}}.validate = function(messageValidator, offset) {
     var err;
 
     err = messageValidator.validateStructHeader(offset, {{struct.name}}.encodedSize, {{struct.packed.packed_fields|length}});
     if (err !== validator.validationError.NONE)
         return err;
 {%-  for packed_field in struct.packed.packed_fields %}
 {%-   set field_name = packed_field.field.name %}
 {%-   if packed_field.field|is_string_pointer_field %}
     // validate {{struct.name}}.{{field_name}}
-    err = messageValidator.validateStringPointer({{packed_field|field_offset}})
+    err = messageValidator.validateStringPointer({{packed_field|validate_string_params}})
 {%-   elif packed_field.field|is_array_pointer_field %}
     // validate {{struct.name}}.{{field_name}}
     err = messageValidator.validateArrayPointer({{packed_field|validate_array_params}});
 {%-   elif packed_field.field|is_struct_pointer_field %}
     // validate {{struct.name}}.{{field_name}}
     err = messageValidator.validateStructPointer({{packed_field|validate_struct_params}});
 {%-   elif packed_field.field|is_handle_field %}
     // validate {{struct.name}}.{{field_name}}
-    err = messageValidator.validateHandle({{packed_field|field_offset}})
+    err = messageValidator.validateHandle({{packed_field|validate_handle_params}})
 {%-   endif %}
     if (err !== validator.validationError.NONE)
         return err;
 {%- endfor %}
 
     return validator.validationError.NONE;
   };
 
 {#--- Encoding and decoding #}
 
@@ skipping 37 matching lines @@
 {%-   else %}
 {%-     for packed_field in byte.packed_fields %}
     encoder.{{packed_field.field.kind|encode_snippet}}val.{{packed_field.field.name}});
 {%-     endfor %}
 {%-   endif %}
 {%-   if byte.is_padding %}
     encoder.skip(1);
 {%-   endif %}
 {%- endfor %}
   };