MD WebUI: Add shared cr-toolbar element

ui/webui/resources/cr_elements/cr_toolbar/cr_toolbar.js

+// Copyright 2016 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: 'cr-toolbar',
+
+  behaviors: [CrSearchFieldBehavior],
+
+  properties: {
+    // Name to display in the toolbar, in titlecase.
+    pageName: String,
+
+    lowerPageName_: {
+      type: String,
+      computed: 'computeLowerPageName_(pageName)'
+    }
+  },
+
+  attached: function() {
+    document.addEventListener('click', this.onDocumentClick_.bind(this));
+  },
+
+  detached: function() {
+    document.removeEventListener('click', this.onDocumentClick_.bind(this));
+  },
+
+  onDocumentClick_: function(e) {

[calamity, 2016/05/16 04:27:34]

Hmmmmm. This is cool but makes me a bit nervous. document.activeElement gives
the 'element keyboard input will go to'.

I don't think will work nicely with input in other pages (e.g clicking a
textfield in settings _should_ defocus the search bar). Even in the history
page, clicking the side menu doesn't defocus the search box.

Can we do onBlur unless hasSearchText_?

[tsergeant, 2016/05/17 03:24:39]

Hmmm, sure. onBlur is way less annoying when you also check hasSearchText. Let's
go with that and see how it is received.

+    // body is active when the user has just clicked off into empty space.
+    if (document.activeElement == document.body && !this.hasSearchText_)
+      this.showingSearch_ = false;
+  },
+
+  showSearch_: function(e) {
+    if (e.target != this.$['clear-search'])
+      this.showingSearch_ = true;
+  },
+
+  computeLowerPageName_: function(name) {
+    return name.toLowerCase();
+  }
+});