Re-scope inner scopes in arrow parameter initializers

test/mjsunit/harmony/regress/regress-4904.js

+// Copyright 2015 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --harmony-do-expressions
+
+(function testCatchScopeInDoExpression() {
+  var f = (s = 17, y = do { try { throw 25; } catch(e) { s += e; }; }) => s;
+  var result = f();
+  assertEquals(result, 42);
+})();
+
+(function testCatchScopeInDoExpression() {
+  var f = (s = 17, y = do { let t; try { throw 25; } catch(e) { s += e; }; }) => s;
+  var result = f();
+  assertEquals(result, 42);
+})();
+
+(function testCatchScopeInDoExpression() {
+  let t1;
+  var f = (s = 17, y = do { let t2; try { throw 25; } catch(e) { s += e; }; }) => s;
+  var result = f();
+  assertEquals(result, 42);
+})();