MD Bookmarks: Add full support for cut/copy/paste keyboard shortcuts

chrome/browser/resources/md_bookmarks/toast_manager.html

 <link rel="import" href="chrome://resources/html/polymer.html">
 
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-button/paper-button.html">
 <link rel="import" href="chrome://bookmarks/shared_style.html">
 
 <dom-module id="bookmarks-toast-manager">
   <template>
     <style include="shared-style">
       #content {
         display: flex;
         flex: 1;
-        margin-right: 32px;
         overflow: hidden;
         text-overflow: ellipsis;
         white-space: nowrap;
       }
 
       paper-button {
+        -webkit-margin-end: 0;
+        -webkit-margin-start: 32px;
         color: var(--google-blue-300);
         font-weight: 500;
         height: 32px;
-        margin: 0;
         min-width: 52px;
         padding: 8px;
       }
 
       .collapsible {
         overflow: hidden;
         text-overflow: ellipsis;
       }
 
       span {
@@ skipping 28 matching lines @@
     </style>
     <div id="toast" aria-live="polite">
       <div id="content"></div>
       <paper-button id="button" hidden$="[[!showUndo_]]" on-tap="onUndoTap_">
         $i18n{undo}
       </paper-button>
     </div>
   </template>
   <script src="chrome://bookmarks/toast_manager.js"></script>
 </dom-module>