Add Data-Saver LayoutTest for Worker and SharedWorker

third_party/WebKit/LayoutTests/http/tests/fetch/chromium/resources/data-saver-worker.php

Index: third_party/WebKit/LayoutTests/http/tests/fetch/chromium/resources/data-saver-worker.php
diff --git a/third_party/WebKit/LayoutTests/http/tests/fetch/chromium/resources/data-saver-worker.php b/third_party/WebKit/LayoutTests/http/tests/fetch/chromium/resources/data-saver-worker.php
new file mode 100644
index 0000000000000000000000000000000000000000..3a8c9d2191011984021c43a9704c418a8b9f6714
--- /dev/null
+++ b/third_party/WebKit/LayoutTests/http/tests/fetch/chromium/resources/data-saver-worker.php
@@ -0,0 +1,33 @@
+<?php
+header('Content-Type: text/javascript');
+echo 'var result = {};' . "\n";
+echo 'result["worker_script_header"] = ';
+if (isset($_SERVER['HTTP_SAVE_DATA'])) {
+    echo '"Save-Data: ' . $_SERVER['HTTP_SAVE_DATA'] . '";' . "\n";
+} else {
+    echo '"No Save-Data";' . "\n";
+}
+?>
+
+var CHECK_PATH = './check-save-data-header.php';
+var METHODS = ['GET', 'POST', 'PUT'];
+var REQUESTS =
+    METHODS.map(method => new Request(CHECK_PATH, {method: method}));
+
+if (!self.postMessage) {
+  // For Shared Worker
+  var postMessagePromise =
+      new Promise(resolve => { self.postMessage = resolve; });
+  self.addEventListener('connect', event => {
+    postMessagePromise.then(data => event.ports[0].postMessage(data));
+  });
+}
+
+Promise.all(REQUESTS.map(request => fetch(request)))
+  .then(responses => Promise.all(responses.map(response => response.text())))
+  .then(texts => {
+      for (var i = 0; i < METHODS.length; ++i) {
+        result[METHODS[i]] = texts[i];
+      }
+      self.postMessage(result);
+    });