Fix IsBaseOf in output_traits.h.

ppapi/cpp/output_traits.h

Index: ppapi/cpp/output_traits.h
diff --git a/ppapi/cpp/output_traits.h b/ppapi/cpp/output_traits.h
index 963f296cc2ad63758be8866543dd5276a67f3c0e..186f0da52fd45ac73a68a1379610932a52e49db9 100644
--- a/ppapi/cpp/output_traits.h
+++ b/ppapi/cpp/output_traits.h
@@ -35,6 +35,11 @@ template<typename A> struct IsSame<A, A> {
   static bool const value = true;
 };
 template<typename Base, typename Derived> struct IsBaseOf {
+  // This class doesn't work correctly with forward declarations.
+  // Because sizeof cannot be applied to incomplete types, this line prevents us
+  // from passing in forward declarations.
+  typedef char (*EnsureTypesAreComplete)[sizeof(Base) + sizeof(Derived)];

[dmichael (off chromium), 2012/04/12 16:09:35]

might as well put this in a private section. (actually, everything but value
could be private)

[yzshen1, 2012/04/12 16:30:46]

Done. Thanks!

The public section doesn't come first, because most of the private section
(except the line I just added) has to be above the value definition.

On 2012/04/12 16:09:35, dmichael wrote:

+
   static Derived* CreateDerived();
   static char (&Check(Base*))[1];
   static char (&Check(...))[2];