Fix a number of tests that incorrectly used assertUnreachable.

test/mjsunit/strict-mode.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 824 matching lines @@
   var name = "prop" + "erty"; // to avoid symbol path.
   var o = {};
   Object.defineProperty(o, "property", { value: 7 });
 
   function strict(o, name) {
     "use strict";
     o[name] = "new value";
   }
 
   for (var i = 0; i < 10; i ++) {
+    var exception = false;
     try {
       strict(o, name);
-      assertUnreachable();
     } catch(e) {
+      exception = true;
       assertInstanceof(e, TypeError);
     }
+    assertTrue(exception);
   }
 })();
 
 
 // Specialized KeyedStoreIC experiencing miss.
 (function testKeyedStoreICStrict() {
   var o = [9,8,7,6,5,4,3,2,1];
 
   function test(o, i, v) {
     "use strict";
@@ skipping 318 matching lines @@
     assertEquals(test(i), true);
   }
 })();
 
 
 (function TestStrictModeEval() {
   "use strict";
   eval("var eval_local = 10;");
   assertThrows(function() { return eval_local; }, ReferenceError);
 })();