Mojo C++ bindings: share DataView class between chromium and blink variants.

mojo/public/tools/bindings/generators/cpp_templates/struct_serialization_definition.tmpl

-{%- import "struct_macros.tmpl" as struct_macros %}
-{%- set mojom_type = struct|get_qualified_name_for_kind %}
-
-// static
-bool StructTraits<{{mojom_type}}::DataView, {{mojom_type}}Ptr>::Read(
-    {{mojom_type}}::DataView input,
-    {{mojom_type}}Ptr* output) {
-  bool success = true;
-  {{mojom_type}}Ptr result({{mojom_type}}::New());
-  {{struct_macros.deserialize(struct, "input", "result->%s",
-                              "success")|indent(4)}}
-  *output = std::move(result);
-  return success;
-}