Update testharness.js and idlharness.js.

third_party/WebKit/LayoutTests/external/wpt/resources/testharness.js

 /*global self*/
 /*jshint latedef: nofunc*/
 /*
 Distributed under both the W3C Test Suite License [1] and the W3C
 3-clause BSD License [2]. To contribute to a W3C Test Suite, see the
 policies and contribution forms [3].
 
 [1] http://www.w3.org/Consortium/Legal/2008/04-testsuite-license
 [2] http://www.w3.org/Consortium/Legal/2008/03-bsd-license
 [3] http://www.w3.org/2004/10/27-testcases
@@ skipping 1160 matching lines @@
     {
         try {
             func.call(this);
             assert(false, "assert_throws", description,
                    "${func} did not throw", {func:func});
         } catch (e) {
             if (e instanceof AssertionError) {
                 throw e;
             }
             if (code === null) {
-                return;
+                throw new AssertionError('Test bug: need to pass exception to assert_throws()');
             }
             if (typeof code === "object") {
                 assert(typeof e == "object" && "name" in e && e.name == code.name,
                        "assert_throws", description,
                        "${func} threw ${actual} (${actual_name}) expected ${expected} (${expected_name})",
                                     {func:func, actual:e, actual_name:e.name,
                                      expected:code,
                                      expected_name:code.name});
                 return;
             }
@@ skipping 1592 matching lines @@
         done();
     };
 
     addEventListener("error", error_handler, false);
     addEventListener("unhandledrejection", function(e){ error_handler(e.reason); }, false);
 
     test_environment.on_tests_ready();
 
 })();
 // vim: set expandtab shiftwidth=4 tabstop=4: