Pull in the latest upstream testharness.js changes.

LayoutTests/http/tests/cachestorage/script-tests/cache-match.js

 if (self.importScripts) {
     importScripts('/resources/testharness.js');
     importScripts('/resources/testharness-helpers.js');
     importScripts('../resources/test-helpers.js');
 }
 
 // A set of Request/Response pairs to be used with prepopulated_cache_test().
 var simple_entries = [
   {
     name: 'a',
@@ skipping 432 matching lines @@
           return result.text();
         })
       .then(function(body_text) {
           assert_equals(body_text, 'a simple text file\n',
                         'Cache.match should return a Response object with a ' +
                         'valid body each time it is called.');
         });
   }, 'Cache.match invoked multiple times for the same Request/Response');
 
 prepopulated_cache_test(simple_entries, function(cache, entries) {
-    var request = new Request(entries.a.request, {method: 'POST'});
+    var request = new Request(entries.a.request.clone(), {method: 'POST'});

[jsbell, 2015/07/09 23:44:37]

Rebase to eliminate this diff. :)

     return cache.match(request)
       .then(function(result) {
           assert_equals(result, undefined,
                         'Cache.match should not find a match');
       });
   }, 'Cache.match with POST Request');
 
 prepopulated_cache_test(simple_entries, function(cache, entries) {
     var response = entries.non_2xx_response.response;
     return cache.match(entries.non_2xx_response.request.url)
@@ skipping 44 matching lines @@
           assert_equals(Object.keys(hash).length, entries.length);
         });
 
       return p.then(function() {
           return test_function(cache, hash);
         });
     }, description);
 }
 
 done();