Redesign change screen on new REST API

The new screen exists at #/c2/<id> as it is missing a large number of
features.  The proposal is to include the screen as-is and iterate in
tree, similar to the CodeMirror work.  This allows power users to
start trying the screen out by editing the URL.

Missing features:
- Add reviewer(s)
- Remove reviewer(s)
- Edit commit message
- Diff files in two patch sets
- Dependencies and dependents
- Download links by URL and action (cherry-pick, checkout, etc.)

Change-Id: Ie957fb85c873d044c947000f0f0207a66f87c784

gerrit-gwtui/src/main/java/com/google/gerrit/client/change/ActionMessageBox.java

@@ -0,0 +1,104 @@
+// Copyright (C) 2013 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.client.change;
+
+import com.google.gwt.core.client.GWT;
+import com.google.gwt.event.dom.client.ClickEvent;
+import com.google.gwt.event.dom.client.KeyCodes;
+import com.google.gwt.event.dom.client.KeyPressEvent;
+import com.google.gwt.event.logical.shared.CloseEvent;
+import com.google.gwt.event.logical.shared.CloseHandler;
+import com.google.gwt.resources.client.CssResource;
+import com.google.gwt.uibinder.client.UiBinder;
+import com.google.gwt.uibinder.client.UiField;
+import com.google.gwt.uibinder.client.UiHandler;
+import com.google.gwt.user.client.ui.Button;
+import com.google.gwt.user.client.ui.Composite;
+import com.google.gwt.user.client.ui.HTMLPanel;
+import com.google.gwt.user.client.ui.PopupPanel;
+import com.google.gwtexpui.globalkey.client.GlobalKey;
+import com.google.gwtexpui.globalkey.client.NpTextArea;
+import com.google.gwtexpui.user.client.PluginSafePopupPanel;
+
+abstract class ActionMessageBox extends Composite {
+  interface Binder extends UiBinder<HTMLPanel, ActionMessageBox> {}
+  private static Binder uiBinder = GWT.create(Binder.class);
+
+  static interface Style extends CssResource {
+    String popup();
+  }
+
+  private final Button activatingButton;
+  private PluginSafePopupPanel popup;
+
+  @UiField Style style;
+  @UiField NpTextArea message;
+  @UiField Button send;
+
+  ActionMessageBox(Button button) {
+    this.activatingButton = button;
+    initWidget(uiBinder.createAndBindUi(this));
+    send.setText(button.getText());
+  }
+
+  abstract void send(String message);
+
+  void show() {
+    if (popup != null) {
+      popup.hide();
+      popup = null;
+      return;
+    }
+
+    final PluginSafePopupPanel p = new PluginSafePopupPanel(true);
+    p.setStyleName(style.popup());
+    p.addAutoHidePartner(activatingButton.getElement());
+    p.addCloseHandler(new CloseHandler<PopupPanel>() {
+      @Override
+      public void onClose(CloseEvent<PopupPanel> event) {
+        if (popup == p) {
+          popup = null;
+        }
+      }
+    });
+    p.add(this);
+    p.showRelativeTo(activatingButton);
+    GlobalKey.dialog(p);
+    message.setFocus(true);
+    popup = p;
+  }
+
+  void hide() {
+    if (popup != null) {
+      popup.hide();
+      popup = null;
+    }
+  }
+
+  @UiHandler("message")
+  void onMessageKey(KeyPressEvent event) {
+    if ((event.getCharCode() == '\n' || event.getCharCode() == KeyCodes.KEY_ENTER)
+        && event.isControlKeyDown()) {
+      event.preventDefault();
+      event.stopPropagation();
+      onSend(null);
+    }
+  }
+
+  @UiHandler("send")
+  void onSend(ClickEvent e) {
+    send(message.getValue().trim());
+  }
+}