Add class id to debugger stack trace

runtime/include/dart_debugger_api.h

Index: runtime/include/dart_debugger_api.h
===================================================================
--- runtime/include/dart_debugger_api.h	(revision 35210)
+++ runtime/include/dart_debugger_api.h	(working copy)
@@ -479,6 +479,18 @@
 
 
 /**
+ * Returns origin class of a function.
+ *
+ * Requires there to be a current isolate.
+ * 
+ * \return Returns the class id (a handle to an integer) of the class in
+ * which \function is defined. Returns a null handle if \function is defined
+ * at the top level. Returns an error object otherwise.
+ */
+DART_EXPORT Dart_Handle Dart_GetFunctionOrigin(Dart_Handle function);
+
+
+/**
  * Returns an array containing all the global variable names and values of
  * the library with given \library_id.
  *