Add a ConvertableToTraceFormat type to the trace framework.

ppapi/shared_impl/ppb_trace_event_impl.cc

Index: ppapi/shared_impl/ppb_trace_event_impl.cc
diff --git a/ppapi/shared_impl/ppb_trace_event_impl.cc b/ppapi/shared_impl/ppb_trace_event_impl.cc
index 439bbd446576daf8e5d3f58c64158ace154a44b6..04c13fd3cbaccf3a46d9cee3e4a29f196be5e18d 100644
--- a/ppapi/shared_impl/ppb_trace_event_impl.cc
+++ b/ppapi/shared_impl/ppb_trace_event_impl.cc
@@ -43,7 +43,7 @@ void TraceEventImpl::AddTraceEvent(int8_t phase,
       // an unsigned long int, but trace_event internals are hermetic and
       // accepts an |unsigned long long*|.  The pointer types are compatible but
       // the compiler throws an error without an explicit cast.
-      reinterpret_cast<const unsigned long long*>(arg_values), flags);
+      reinterpret_cast<const unsigned long long*>(arg_values), NULL, flags);
 }
 
 // static