mojo: Mark DataView readers as WARN_UNUSED_RESULT.

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

 // Copyright 2016 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.
 
 {%- set header_guard = "%s_SHARED_H_"|format(
         module.path|upper|replace("/","_")|replace(".","_")|
             replace("-", "_")) %}
 
 {%- macro mojom_type_traits(kind) %}
 template <>
@@ skipping 24 matching lines @@
 #ifndef {{header_guard}}
 #define {{header_guard}}
 
 #include <stdint.h>
 
 #include <functional>
 #include <ostream>
 #include <type_traits>
 #include <utility>
 
+#include "base/compiler_specific.h"
 #include "mojo/public/cpp/bindings/array_data_view.h"
 #include "mojo/public/cpp/bindings/enum_traits.h"
 #include "mojo/public/cpp/bindings/interface_data_view.h"
 #include "mojo/public/cpp/bindings/lib/bindings_internal.h"
 #include "mojo/public/cpp/bindings/lib/serialization.h"
 #include "mojo/public/cpp/bindings/map_data_view.h"
 #include "mojo/public/cpp/bindings/native_enum.h"
 #include "mojo/public/cpp/bindings/native_struct_data_view.h"
 #include "mojo/public/cpp/bindings/string_data_view.h"
 #include "{{module.path}}-shared-internal.h"
@@ skipping 147 matching lines @@
 {%- endfor %}
 
 {%- for union in unions %}
 {%    include "union_data_view_definition.tmpl" %}
 {%- endfor %}
 
 {{namespace_end()}}
 
 #endif  // {{header_guard}}