Only swap undefined for the global object if necessary in the prologue

src/compiler.cc

Index: src/compiler.cc
diff --git a/src/compiler.cc b/src/compiler.cc
index ada773c3861eb177629de03f60cc279d8eb2518e..2ad1ff447e26d51a7b4750ab979e8a9b96d0a1bb 100644
--- a/src/compiler.cc
+++ b/src/compiler.cc
@@ -214,6 +214,12 @@ bool CompilationInfo::is_simple_parameter_list() {
 }
 
 
+bool CompilationInfo::MayUseThis() const {
+  return scope()->uses_this() || scope()->inner_uses_this() ||
+         scope()->calls_sloppy_eval();
+}
+
+
 int CompilationInfo::TraceInlinedFunction(Handle<SharedFunctionInfo> shared,
                                           SourcePosition position,
                                           int parent_id) {