Use a different map to distinguish eval contexts

src/factory.h

Index: src/factory.h
diff --git a/src/factory.h b/src/factory.h
index e8d4a3a5d4ef307d9f3ef5bf065e76895c23c585..97e8ea469f3b5d371511f377069298cebe10b676 100644
--- a/src/factory.h
+++ b/src/factory.h
@@ -288,6 +288,9 @@ class V8_EXPORT_PRIVATE Factory final {
   // Create a function context.
   Handle<Context> NewFunctionContext(int length, Handle<JSFunction> function);
 
+  // Create a eval context.
+  Handle<Context> NewEvalContext(int length, Handle<JSFunction> function);
+
   // Create a catch context.
   Handle<Context> NewCatchContext(Handle<JSFunction> function,
                                   Handle<Context> previous,