Protect against uninitialized lexical variables at top-level.

test/cctest/test-decls.cc

 // Copyright 2007-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1127 matching lines @@
     context.Check("'use strict';const x = 1; x", EXPECT_RESULT,
                   Number::New(CcTest::isolate(), 1));
     context.Check("f();", EXPECT_EXCEPTION);
     context.Check("x", EXPECT_RESULT, Number::New(CcTest::isolate(), 1));
     context.Check("f();", EXPECT_EXCEPTION);
     context.Check("x", EXPECT_RESULT, Number::New(CcTest::isolate(), 1));
     context.Check("%OptimizeFunctionOnNextCall(f);f();", EXPECT_EXCEPTION);
     context.Check("x", EXPECT_RESULT, Number::New(CcTest::isolate(), 1));
   }
 }
+
+
+TEST(Regress425510) {
+  i::FLAG_harmony_scoping = true;
+  i::FLAG_allow_natives_syntax = true;
+
+  HandleScope handle_scope(CcTest::isolate());
+
+  {
+    SimpleContext context;
+
+    context.Check("'use strict'; o; const o = 10", EXPECT_EXCEPTION);
+
+    for (int i = 0; i < 100; i++) {
+      context.Check("o.prototype", EXPECT_EXCEPTION);
+    }
+  }
+}