Harden Function()'s parsing of function literals.

src/parser.cc

Index: src/parser.cc
diff --git a/src/parser.cc b/src/parser.cc
index 62b633ea2807f4edbfed4d6147196058f3745ec9..2b2cf65d1f2fc5b4ec61474fb227fc9ee98e0e5a 100644
--- a/src/parser.cc
+++ b/src/parser.cc
@@ -656,6 +656,16 @@ FunctionLiteral* Parser::DoParseProgram(CompilationInfo* info,
       CheckConflictingVarDeclarations(top_scope_, &ok);
     }
 
+    if (ok && info->parse_restriction() == ONLY_SINGLE_FUNCTION_LITERAL) {
+      if (body->length() != 1 ||
+          !body->at(0)->IsExpressionStatement() ||
+          !body->at(0)->AsExpressionStatement()->
+              expression()->IsFunctionLiteral()) {
+        ReportMessage("unable_to_parse", Vector<const char*>::empty());
+        ok = false;
+      }
+    }
+
     if (ok) {
       result = factory()->NewFunctionLiteral(
           no_name,