Detect conflicting variable bindings in harmony mode.

test/mjsunit/harmony/block-let-declaration.js

Index: test/mjsunit/harmony/block-let-declaration.js
diff --git a/test/mjsunit/harmony/block-let-declaration.js b/test/mjsunit/harmony/block-let-declaration.js
index 19c943f14c0b1313c842f21ee7dc090d1a812b12..49b63481a0bf025de0566fe21455e2f0bc185808 100644
--- a/test/mjsunit/harmony/block-let-declaration.js
+++ b/test/mjsunit/harmony/block-let-declaration.js
@@ -57,11 +57,9 @@ function TestLocalDoesNotThrow(str) {
 
 // Unprotected statement
 TestLocalThrows("if (true) let x;", SyntaxError);
-TestLocalThrows("with ({}) let x;", SyntaxError);
 TestLocalThrows("do let x; while (false)", SyntaxError);
 TestLocalThrows("while (false) let x;", SyntaxError);
 
 TestLocalDoesNotThrow("if (true) var x;");
-TestLocalDoesNotThrow("with ({}) var x;");
 TestLocalDoesNotThrow("do var x; while (false)");
 TestLocalDoesNotThrow("while (false) var x;");