Merge up to 8597 to experimental/gc from the bleeding edge.

test/mjsunit/compiler/regress-const.js

 // Copyright 2011 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 48 matching lines @@
   const X = 42;
   return r + X;
 }
 
 for (var i = 0; i < 5; i++) h(1,2);
 
 %OptimizeFunctionOnNextCall(h);
 
 assertEquals(45, h(1,2));
 assertEquals("foo742", h("foo", 7));