MD History: Hook all elements into the page and add tests.

chrome/browser/resources/md_history/history_toolbar.js

Index: chrome/browser/resources/md_history/history_toolbar.js
diff --git a/chrome/browser/resources/md_history/history_toolbar.js b/chrome/browser/resources/md_history/history_toolbar.js
new file mode 100644
index 0000000000000000000000000000000000000000..7339c516daf92daab305ef90c8ad6a948541c0af
--- /dev/null
+++ b/chrome/browser/resources/md_history/history_toolbar.js
@@ -0,0 +1,35 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+Polymer({
+  is: 'history-toolbar',
+  properties: {
+    // Number of history items currently selected.
+    count: {
+      type: Number,
+      value: 0,
+      observer: 'changeToolbarView_'
+    },
+    // True if 1 or more history items are selected. When this value changes
+    // the background colour changes.
+    itemsSelected_: {
+      type: Boolean,
+      value: false,
+      reflectToAttribute: true
+    }
+  },
+
+  /**
+   * This function changes the toolbar background color depending on whether or
+   * not any history items are currently selected.
+   * @private
+   */
+  changeToolbarView_: function() {
+    this.itemsSelected_ = this.count != 0;
+  },
+
+  clearSelection: function() {
+    this.fire('unselect-all');
+  }
+});