Pass strict mode flag to eval.

src/scopes.cc

Index: src/scopes.cc
diff --git a/src/scopes.cc b/src/scopes.cc
index d3f54ad3f2d9ad8b47fefae2d89fd692bd3e2eda..e23e1cbe2292eb3d35f65517c36c6b8eb7bf651f 100644
--- a/src/scopes.cc
+++ b/src/scopes.cc
@@ -490,6 +490,13 @@ int Scope::ContextChainLength(Scope* scope) {
   return n;
 }
 
+// In strict mode, arguments are const.
+void Scope::SetAttributesConst() {
+  Variable* arguments = LocalLookup(Factory::arguments_symbol());
+  ASSERT(arguments != NULL);  // functions have 'arguments' declared implicitly
+  ASSERT(arguments->mode() == Variable::VAR);
+  arguments->set_mode(Variable::CONST);
+}
 
 #ifdef DEBUG
 static const char* Header(Scope::Type type) {