Mojo C++ bindings: switch the existing usage of StructTraits to use the new data view interface.

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

Index: mojo/public/tools/bindings/generators/cpp_templates/module.h.tmpl
diff --git a/mojo/public/tools/bindings/generators/cpp_templates/module.h.tmpl b/mojo/public/tools/bindings/generators/cpp_templates/module.h.tmpl
index 85b8d6bd5f2841b91d7a6aa81e8bc7b5b4e81720..a600f531f70344e5bca4f48b787c4f12f63b0008 100644
--- a/mojo/public/tools/bindings/generators/cpp_templates/module.h.tmpl
+++ b/mojo/public/tools/bindings/generators/cpp_templates/module.h.tmpl
@@ -125,7 +125,6 @@ using {{struct.name}} = mojo::NativeStruct;
 using {{struct.name}}Ptr = mojo::NativeStructPtr;
 {%-   else %}
 class {{struct.name}};
-class {{struct.name}}_Reader;
 class {{struct.name}}DataView;
 {%-     if struct|should_inline %}
 using {{struct.name}}Ptr = mojo::InlinedStructPtr<{{struct.name}}>;