Adding ArrayBuffer support to ServiceWorker Response and tests

LayoutTests/http/tests/serviceworker/resources/response-content-worker.js

+importScripts('worker-test-harness.js');
+
+promise_test(function() {
+    var response = new Response('test string');
+    assert_equals(
+      response.headers.get('Content-Type'),
+      'text/plain;charset=UTF-8',
+      'A Response constructed with a string should have a Content-Type.');
+    return response.body.asText()
+      .then(function(text) {
+          assert_equals(text, 'test string',
+            'Response body text should match the string on construction.');
+        });
+  }, 'Behavior of Response with string content.');
+
+promise_test(function() {
+    var intView  = new Int32Array([0, 1, 2, 3, 4, 55, 6, 7, 8, 9]);
+    var buffer = intView.buffer;
+
+    var response = new Response(buffer);
+    assert_false(response.headers.has('Content-Type'),
+      'A Response constructed with ArrayBuffer should not have a content type.');
+    return response.body.asArrayBuffer()
+      .then(function(buffer) {
+          var resultIntView = new Int32Array(buffer);
+          assert_array_equals(
+            resultIntView, [0, 1, 2, 3, 4, 55, 6, 7, 8, 9],
+            'Response body ArrayBuffer should match ArrayBuffer ' +
+            'it was constructed with.');
+        });
+  }, 'Behavior of Response with arraybuffer content.');