Support all fast elements kinds in the major array operations.

test/mjsunit/elements-kind.js

 // Copyright 2012 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 303 matching lines @@
 }
 
 // Test if Array.concat() works correctly with DOUBLE elements.
 if (support_smi_only_arrays) {
   var a = [1, 2];
   assertKind(elements_kind.fast_smi_only, a);
   var b = [4.5, 5.5];
   assertKind(elements_kind.fast_double, b);
   var c = a.concat(b);
   assertEquals([1, 2, 4.5, 5.5], c);
-  // TODO(1810): Change implementation so that we get DOUBLE elements here?
-  assertKind(elements_kind.fast, c);
+  assertKind(elements_kind.fast_double, c);
 }
 
 // Test that Array.push() correctly handles SMI elements.
 if (support_smi_only_arrays) {
   var a = [1, 2];
   assertKind(elements_kind.fast_smi_only, a);
   a.push(3, 4, 5);
   assertKind(elements_kind.fast_smi_only, a);
   assertEquals([1, 2, 3, 4, 5], a);
 }
 
 // Test that Array.splice() and Array.slice() return correct ElementsKinds.
 if (support_smi_only_arrays) {
   var a = ["foo", "bar"];
   assertKind(elements_kind.fast, a);
   var b = a.splice(0, 1);
   assertKind(elements_kind.fast, b);
   var c = a.slice(0, 1);
   assertKind(elements_kind.fast, c);
 }
 
 // Throw away type information in the ICs for next stress run.
 gc();