Use md-select instead of paper-dropdown-menu-light in display.html

chrome/browser/resources/settings/device_page/display.js

Index: chrome/browser/resources/settings/device_page/display.js
diff --git a/chrome/browser/resources/settings/device_page/display.js b/chrome/browser/resources/settings/device_page/display.js
index 5b83b075579f10bada5cda397170860ad90c5332..89ca0bcb0da60e91b102b699bb53c12ba57802e0 100644
--- a/chrome/browser/resources/settings/device_page/display.js
+++ b/chrome/browser/resources/settings/device_page/display.js
@@ -154,10 +154,12 @@ Polymer({
     if (this.selectedDisplay.modes.length == 0) {
       this.maxModeIndex_ = 0;
       this.selectedModeIndex_ = 0;
-      return;
+    } else {
+      this.maxModeIndex_ = this.selectedDisplay.modes.length - 1;
+      this.selectedModeIndex_ =
+          this.getSelectedModeIndex_(this.selectedDisplay);
     }
-    this.maxModeIndex_ = this.selectedDisplay.modes.length - 1;
-    this.selectedModeIndex_ = this.getSelectedModeIndex_(this.selectedDisplay);
+    this.$.orientation.value = this.selectedDisplay.rotation;

[dpapad, 2016/10/18 00:14:46]

Nit: Since your drodpown is not using dom-repeat, you can use 1-way data binding
without any worries here (all <option> instances are rendered in when ready() is
called). So no need to programmatically set the value.

<select .... value="[[this.selectedDisplay.rotation]]">

[stevenjb, 2016/10/18 00:43:11]

Yup. I just finished making this consistent with the internet changes.

   },
 
   /**
@@ -279,12 +281,12 @@ Polymer({
   },
 
   /**
-   * @param {!{detail: !{selected: string}}} e
+   * @param {!{target: !{value: string}}} e

[dpapad, 2016/10/18 00:14:46]

@param {!Event}

[stevenjb, 2016/10/18 00:43:11]

Acknowledged.

    * @private
    */
   onSetOrientation_: function(e) {
     /** @type {!chrome.system.display.DisplayProperties} */ var properties = {
-      rotation: parseInt(e.detail.selected, 10)
+      rotation: parseInt(e.target.value, 10)

[dpapad, 2016/10/18 00:14:46]

Cast to HTMLSelectElement to satisfy the compiler.

[stevenjb, 2016/10/18 00:43:10]

Acknowledged.

     };
     settings.display.systemDisplayApi.setDisplayProperties(
         this.selectedDisplay.id, properties,