Add a cr-button element, a thin wrapper around paper-button.

ui/webui/resources/cr_elements/cr_button/cr_button.js

Index: ui/webui/resources/cr_elements/cr_button/cr_button.js
diff --git a/ui/webui/resources/cr_elements/cr_button/cr_button.js b/ui/webui/resources/cr_elements/cr_button/cr_button.js
new file mode 100644
index 0000000000000000000000000000000000000000..0a5fe9994e83136690e1823a5007facdf3152117
--- /dev/null
+++ b/ui/webui/resources/cr_elements/cr_button/cr_button.js
@@ -0,0 +1,40 @@
+/* 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. */
+
+/**
+ * @fileoverview
+ * 'cr-button' is a chrome-specific wrapper around paper-button.
+ *
+ * Example:
+ *
+ *    <cr-button>Press Here</cr-button>
+ *    <cr-button raised>Raised Button</cr-button>
+ *    <cr-button>
+        <core-icon icon="favorite"></core-icon> Custom button

[James Hawkins, 2015/02/28 22:21:58]

nit: Missing comment asterisks on the left.

[Jeremy Klein, 2015/02/28 23:58:11]

Nice catch. Done.

+      </cr-button>
+ *
+ * @group Chrome Elements
+ * @element cr-button
+ */
+Polymer('cr-button', {
+  publish: {
+    /**
+     * If true, the button will be styled with a shadow.
+     *
+     * @attribute raised
+     * @type boolean
+     * @default false
+     */
+    raised: {value: false, reflect: true},
+
+    /**
+     * If true, the button will be disabled and greyed out.
+     *
+     * @attribute disabled
+     * @type boolean
+     * @default false
+     */
+    disabled: {value: false, reflect: true},
+  },
+});