Incorrect handling of HTransitionElementsKind in hydrogen check elimination phase fixed.

test/mjsunit/regress/regress-460917.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: --allow-natives-syntax
+
+function boom(a1, a2) {
+  // Do something with a2 that needs a map check (for DOUBLE_ELEMENTS).
+  var s = a2[0];
+  // Emit a load that transitions a1 to FAST_ELEMENTS.
+  var t = a1[0];
+  // Emit a store to a2 that assumes DOUBLE_ELEMENTS.
+  // The map check is considered redundant and will be eliminated.
+  a2[0] = 0.3;
+}
+
+// Prepare type feedback for the "t = a1[0]" load: fast elements.
+var fast_elem = new Array(1);
+fast_elem[0] = "tagged";
+boom(fast_elem, [1]);
+
+// Prepare type feedback for the "a2[0] = 0.3" store: double elements.
+var double_elem = new Array(1);
+double_elem[0] = 0.1;
+boom(double_elem, double_elem);
+
+// Reset |double_elem| and go have a party.
+double_elem = new Array(10);
+double_elem[0] = 0.1;
+
+%OptimizeFunctionOnNextCall(boom);
+boom(double_elem, double_elem);
+
+assertEquals(0.3, double_elem[0]);
+assertEquals(undefined, double_elem[1]);