Mojo C++ bindings: change the first template parameter of StructTraits and UnionTraits.

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}}, {{mojom_type}}Ptr>::Read(
-    {{mojom_type}}DataView input,
+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;
 }