Fix a number of tests that incorrectly used assertUnreachable.

test/mjsunit/object-seal.js

 // Copyright 2010 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 14 matching lines @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 // Tests the Object.seal and Object.isSealed methods - ES 15.2.3.9 and
 // ES 15.2.3.12
 
 
 // Test that we throw an error if an object is not passed as argument.
 var non_objects = new Array(undefined, null, 1, -1, 0, 42.43);
 for (var key in non_objects) {
+  var exception = false;
   try {
     Object.seal(non_objects[key]);
-    assertUnreachable();
   } catch(e) {
+    exception = true;
     assertTrue(/Object.seal called on non-object/.test(e));
   }
+  assertTrue(exception);
 }
 
 for (var key in non_objects) {
+  exception = false;
   try {
     Object.isSealed(non_objects[key]);
-    assertUnreachable();
   } catch(e) {
+    exception = true;
     assertTrue(/Object.isSealed called on non-object/.test(e));
   }
+  assertTrue(exception);
 }
 
 // Test normal data properties.
 var obj = { x: 42, z: 'foobar' };
 var desc = Object.getOwnPropertyDescriptor(obj, 'x');
 assertTrue(desc.writable);
 assertTrue(desc.configurable);
 assertEquals(42, desc.value);
 
 desc = Object.getOwnPropertyDescriptor(obj, 'z');
@@ skipping 121 matching lines @@
 var obj4 = {};
 Object.defineProperty(obj4, 'x', {configurable: true, writable: false});
 Object.defineProperty(obj4, 'y', {configurable: false, writable: false});
 Object.preventExtensions(obj4);
 
 assertFalse(Object.isSealed(obj4));
 
 // Make sure that Object.seal returns the sealed object.
 var obj4 = {};
 assertTrue(obj4 === Object.seal(obj4));