Introduce global contexts to represent lexical global scope(s).

src/factory.h

Index: src/factory.h
diff --git a/src/factory.h b/src/factory.h
index 2dbd91521ddccf7678f0fdb1499870c0f196a0f1..e617abb6d12e8cdde155dc569fd87beb7c2aab1d 100644
--- a/src/factory.h
+++ b/src/factory.h
@@ -162,6 +162,10 @@ class Factory {
   // Create a global (but otherwise uninitialized) context.
   Handle<Context> NewNativeContext();
 
+  // Create a global context.
+  Handle<Context> NewGlobalContext(Handle<JSFunction> function,
+                                   Handle<ScopeInfo> scope_info);
+
   // Create a module context.
   Handle<Context> NewModuleContext(Handle<ScopeInfo> scope_info);