Implement hand tool

The logic for the hand tool is implemented in a separate project,
maintained at https://github.com/Rob--W/grab-to-pan.js

Integration notes
- Added toggle as an entry under the Secondary toolbar
- Added shortcut "h" to toggle hand tool (to-do: document this in wiki
  after merge). This shortcut is also used in Adobe's Acrobat Reader.

To-do: localizations for:
hand_tool_enable.title=
hand_tool_enable_label=
hand_tool_disable.title=
hand_tool_disable_label=

To-do (wish): persistence of hand tool preference, preferably a global setting.

secondaryToolbarButton-handTool.png created by Stephen Horlander <shorlander@mozilla.com>

web/hand_tool.js

@@ -0,0 +1,62 @@
+/* -*- Mode: Java; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set shiftwidth=2 tabstop=2 autoindent cindent expandtab: */
+/* Copyright 2013 Mozilla Foundation
+ *
+ * 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.
+ */
+/* globals mozL10n, GrabToPan, PDFView */
+
+'use strict';
+
+//#include grab_to_pan.js
+var HandTool = {
+  initialize: function handToolInitialize(options) {
+    var toggleHandTool = options.toggleHandTool;
+    this.handTool = new GrabToPan({
+      element: options.container,
+      onActiveChanged: function(isActive) {
+        if (isActive) {
+          toggleHandTool.title =
+            mozL10n.get('hand_tool_disable.title', null, 'Disable hand tool');
+          toggleHandTool.firstElementChild.textContent =
+            mozL10n.get('hand_tool_disable_label', null, 'Disable hand tool');
+        } else {
+          toggleHandTool.title =
+            mozL10n.get('hand_tool_enable.title', null, 'Enable hand tool');
+          toggleHandTool.firstElementChild.textContent =
+            mozL10n.get('hand_tool_enable_label', null, 'Enable hand tool');
+        }
+    }
+    });
+    toggleHandTool.addEventListener('click', this.handTool.toggle, false);
+    // TODO: Read global prefs and call this.handTool.activate() if needed.
+  },
+
+  toggle: function handToolToggle() {
+    this.handTool.toggle();
+  },
+
+  enterPresentationMode: function handToolEnterPresentationMode() {
+    if (this.handTool.active) {
+      this.wasActive = true;
+      this.handTool.deactivate();
+    }
+  },
+
+  exitPresentationMode: function handToolExitPresentationMode() {
+    if (this.wasActive) {
+      this.wasActive = null;
+      this.handTool.activate();
+    }
+  }
+};