WebUI: Remove last usage of paper-material.

chrome/browser/resources/settings/device_page/display_layout.html

 <link rel="import" href="chrome://resources/html/polymer.html">
 
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-resizable-behavior/iron-resizable-behavior.html">
-<link rel="import" href="chrome://resources/polymer/v1_0/paper-material/paper-material-shared-styles.html">
+<link rel="import" href="chrome://resources/polymer/v1_0/paper-styles/shadow.html">
 <link rel="import" href="drag_behavior.html">
 <link rel="import" href="layout_behavior.html">
 <link rel="import" href="../settings_shared_css.html">
 
 <dom-module id="display-layout">
   <template>
-    <style include="settings-shared paper-material-shared-styles">

[dpapad, 2017/06/03 02:19:46]

I had converted <paper-material> usage to paper-material-shared-styles usage at
https://codereview.chromium.org/2885363006, but now I am realizing that the only
dependency we actually need is paper-styles/shadow.html.

+    <style include="settings-shared">
       /* Use relative position with no offset so that display divs (children),
          which have absolute positions, are offset from the displayArea div. */
       #displayArea {
         height: 100%;
         overflow: hidden;
         position: relative;
         width: 100%;
       }
 
       /* Note: the size of the border / box shadow affects the style generated
@@ skipping 47 matching lines @@
             draggable="[[dragEnabled]]" on-tap="onSelectDisplayTap_"
             style$="[[getDivStyle_(item.id, item.bounds, visualScale)]]"
             selected$="[[isSelected_(item, selectedDisplay)]]">
           [[item.name]]
         </div>
       </template>
     </div>
   </template>
   <script src="display_layout.js"></script>
 </dom-module>