Create implementation of the side panel using a dialog.

chrome/browser/resources/settings/controls/dialog_drawer.html

+<link rel="import" href="chrome://resources/html/polymer.html">
+
+<dom-module name="dialog-drawer">
+  <template>
+    <style>
+      :host {
+        background-color: #FFF;
+        border: none;
+        bottom: 0;
+        height: 100%;
+        left: -265px;
+        margin: 0;
+        overflow: hidden;
+        padding: 0;
+        position: absolute;
+        top: 0;
+        transition: left 200ms ease;
+        width: 256px;

[dpapad, 2016/12/08 22:27:22]

What is the relation of 256 and 265 above? Should this be 265 too?

Also can we use a CSS variable wherevere possible, to avoid repeating literal
values?

[hcarmona, 2016/12/09 16:14:42]

Good catch! Yes, both values should be the same. Updated to use a variable.

+      }
+
+      :host(.opening) {
+        left: 0;
+      }
+
+      :host([align=right]) {
+        left: auto;
+        right: -256px;
+        transition: right 200ms ease;
+      }
+
+      :host(.opening[align=right]) {
+        right: 0;
+      }
+
+      :host::backdrop {
+        background: rgba(0, 0, 0, 0.5);
+        bottom: 0;
+        left: 0;
+        opacity: 0;
+        position: absolute;
+        right: 0;
+        top: 0;
+        transition: opacity 200ms ease;
+      }
+
+      :host(.opening)::backdrop {
+        opacity: 1;
+      }
+    </style>
+    <content></content>
+  </template>
+</dom-module>
+<script src="dialog_drawer.js"></script>