Mojo: validate nullability in Java serialization.

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

 {% from "constant_definition.tmpl" import constant_def %}
 {% from "enum_definition.tmpl" import enum_def %}
 
 {%- macro array_expected_length(kind) -%}
 {%- if kind|is_fixed_array_kind -%}
 {{kind.length}}
 {%- else -%}
 org.chromium.mojo.bindings.BindingsHelper.UNSPECIFIED_ARRAY_LENGTH
 {%- endif -%}
 {%- endmacro -%}
 
 {% macro encode(variable, kind, offset, bit, level=0) %}
 {% if kind|is_pointer_array_kind %}
 {% set sub_kind = kind.kind %}
 if ({{variable}} == null) {
-    encoder{{level}}.encodeNullPointer({{offset}});
+    encoder{{level}}.encodeNullPointer({{offset}}, {{kind|is_nullable_kind|java_true_false}});
 } else {
     org.chromium.mojo.bindings.Encoder encoder{{level + 1}} = encoder{{level}}.encodePointerArray({{variable}}.length, {{offset}}, {{array_expected_length(kind)}});
     for (int i{{level}} = 0; i{{level}} < {{variable}}.length; ++i{{level}}) {
         {{encode(variable~'[i'~level~']', sub_kind, 'DataHeader.HEADER_SIZE + org.chromium.mojo.bindings.BindingsHelper.POINTER_SIZE * i'~level, 0, level+1)|indent(8)}}
     }
 }
 {% else %}
 encoder{{level}}.{{kind|encode_method(variable, offset, bit)}};
 {% endif %}
 {% endmacro %}
@@ skipping 82 matching lines @@
         org.chromium.mojo.bindings.Encoder encoder0 = encoder.getEncoderAtDataOffset(DEFAULT_STRUCT_INFO);
 {% endif %}
 {% for byte in struct.bytes %}
 {%   for packed_field in byte.packed_fields %}
         {{encode(packed_field.field|name, packed_field.field.kind, 8+packed_field.offset, packed_field.bit)|indent(8)}}
 {%   endfor %}
 {% endfor %}
     }
 }
 {% endmacro %}