Added base template for config ui.

appengine/config_service/ui/bower_components/polymer/lib/utils/import-href.html

+<!--
+@license
+Copyright (c) 2017 The Polymer Project Authors. All rights reserved.
+This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
+The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
+The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
+Code distributed by Google as part of the polymer project is also
+subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
+-->
+
+<link rel="import" href="boot.html">
+
+<script>
+
+(function() {
+
+  'use strict';
+
+  // run a callback when HTMLImports are ready or immediately if
+  // this api is not available.
+  function whenImportsReady(cb) {
+    if (window.HTMLImports) {
+      HTMLImports.whenReady(cb);
+    } else {
+      cb();
+    }
+  }
+
+  /**
+   * Convenience method for importing an HTML document imperatively.
+   *
+   * This method creates a new `<link rel="import">` element with
+   * the provided URL and appends it to the document to start loading.
+   * In the `onload` callback, the `import` property of the `link`
+   * element will contain the imported document contents.
+   *
+   * @memberof Polymer
+   * @param {string} href URL to document to load.
+   * @param {Function=} onload Callback to notify when an import successfully
+   *   loaded.
+   * @param {Function=} onerror Callback to notify when an import
+   *   unsuccessfully loaded.
+   * @param {boolean=} optAsync True if the import should be loaded `async`.
+   *   Defaults to `false`.
+   * @return {HTMLLinkElement} The link element for the URL to be loaded.
+   */
+  Polymer.importHref = function(href, onload, onerror, optAsync) {
+    let link =
+      document.head.querySelector('link[href="' + href + '"][import-href]');
+    if (!link) {
+      link = document.createElement('link');
+      link.rel = 'import';
+      link.href = href;
+      link.setAttribute('import-href', '');
+    }
+    // always ensure link has `async` attribute if user specified one,
+    // even if it was previously not async. This is considered less confusing.
+    if (optAsync) {
+      link.setAttribute('async', '');
+    }
+    // NOTE: the link may now be in 3 states: (1) pending insertion,
+    // (2) inflight, (3) already laoded. In each case, we need to add
+    // event listeners to process callbacks.
+    let cleanup = function() {
+      link.removeEventListener('load', loadListener);
+      link.removeEventListener('error', errorListener);
+    }
+    let loadListener = function(event) {
+      cleanup();
+      // In case of a successful load, cache the load event on the link so
+      // that it can be used to short-circuit this method in the future when
+      // it is called with the same href param.
+      link.__dynamicImportLoaded = true;
+      if (onload) {
+        whenImportsReady(() => {
+          onload(event);
+        });
+      }
+    };
+    let errorListener = function(event) {
+      cleanup();
+      // In case of an error, remove the link from the document so that it
+      // will be automatically created again the next time `importHref` is
+      // called.
+      if (link.parentNode) {
+        link.parentNode.removeChild(link);
+      }
+      if (onerror) {
+        whenImportsReady(() => {
+          onerror(event);
+        });
+      }
+    };
+    link.addEventListener('load', loadListener);
+    link.addEventListener('error', errorListener);
+    if (link.parentNode == null) {
+      document.head.appendChild(link);
+    // if the link already loaded, dispatch a fake load event
+    // so that listeners are called and get a proper event argument.
+    } else if (link.__dynamicImportLoaded) {
+      link.dispatchEvent(new Event('load'));
+    }
+    return link;
+  };
+
+})();
+</script>