Expose the calling context through the API. ...

src/top.h

Index: src/top.h
===================================================================
--- src/top.h	(revision 2003)
+++ src/top.h	(working copy)
@@ -255,8 +255,13 @@
     return context()->global_proxy();
   }
 
+  // Returns the current global context.
   static Handle<Context> global_context();
 
+  // Returns the global context of the calling JavaScript code.  That
+  // is, the global context of the top-most JavaScript frame.
+  static Handle<Context> GetCallingGlobalContext();
+
   static Handle<JSBuiltinsObject> builtins() {
     return Handle<JSBuiltinsObject>(thread_local_.context_->builtins());
   }