MD History: Show sidebar next to content on wide screens

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

Index: ui/webui/resources/cr_elements/cr_toolbar/cr_toolbar.js
diff --git a/ui/webui/resources/cr_elements/cr_toolbar/cr_toolbar.js b/ui/webui/resources/cr_elements/cr_toolbar/cr_toolbar.js
index b119b9e05fcbd3ab382694598ffd2668fd70e94d..876b934abd01b658b5547124aa8b3bacb3ff4802 100644
--- a/ui/webui/resources/cr_elements/cr_toolbar/cr_toolbar.js
+++ b/ui/webui/resources/cr_elements/cr_toolbar/cr_toolbar.js
@@ -19,6 +19,13 @@ Polymer({
     // the search field will show a processing spinner.
     spinnerActive: Boolean,
 
+    // Controls whether the menu button is shown at the start of the menu.
+    showMenu: {
+      type: Boolean,
+      reflectToAttribute: true,
+      value: true
+    },
+
     /** @private */
     narrow_: {
       type: Boolean,