Allow UiActions to perform redirects without JavaScript

This is a simple approach to enable a GET based UiAction to send a
redirect to the browser to either replace Gerrit or open a new window
without writing JavaScript.

Change-Id: I38ca4bbad1ccf4a9ff376d17243b9d445abed537

gerrit-extension-api/src/main/java/com/google/gerrit/extensions/webui/UiResult.java

@@ -0,0 +1,59 @@
+// Copyright (C) 2014 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.extensions.webui;
+
+import java.net.URI;
+
+/** Default result for {@link UiAction}s with no JavaScript. */
+public class UiResult {
+  /** Display an alert message to the user. */
+  public static UiResult alert(String message) {
+    UiResult r = new UiResult();
+    r.alert = message;
+    return r;
+  }
+
+  /** Launch URL in a new window. */
+  public static UiResult openUrl(URI uri) {
+    return openUrl(uri.toString());
+  }
+
+  /** Launch URL in a new window. */
+  public static UiResult openUrl(String url) {
+    UiResult r = new UiResult();
+    r.url = url;
+    r.openWindow = true;
+    return r;
+  }
+
+  /** Redirect the browser to a new URL. */
+  public static UiResult redirectUrl(String url) {
+    UiResult r = new UiResult();
+    r.url = url;
+    return r;
+  }
+
+  /** Alert the user with a message. */
+  protected String alert;
+
+  /** If present redirect browser to this URL. */
+  protected String url;
+
+  /** When true open {@link #url} in a new tab/window. */
+  protected Boolean openWindow;
+
+  private UiResult() {
+  }
+}