Import w3c tests for the service workers

third_party/WebKit/LayoutTests/imported/wpt/service-workers/service-worker/resources/request-end-to-end-worker.js

+var port = undefined;
+
+onmessage = function(e) {
+  var message = e.data;
+  if (typeof message === 'object' && 'port' in message) {
+    port = message.port;
+  }
+};
+
+onfetch = function(e) {
+  var headers = {};
+  var errorNameWhileAppendingHeader;
+  for (var header of e.request.headers) {
+    var key = header[0], value = header[1];
+    headers[key] = value;
+  }
+  var errorNameWhileAddingHeader = '';
+  try {
+    e.request.headers.append('Test-Header', 'TestValue');
+  } catch (e) {
+    errorNameWhileAppendingHeader = e.name;
+  }
+  port.postMessage({
+      url: e.request.url,
+      mode: e.request.mode,
+      method: e.request.method,
+      referrer: e.request.referrer,
+      headers: headers,
+      headerSize: e.request.headers.size,
+      errorNameWhileAppendingHeader: errorNameWhileAppendingHeader
+    });
+};