MD Settings: App drawer, remove TODO about waterfall effect.

chrome/browser/resources/settings/settings_ui/settings_ui.html

 <link rel="import" href="chrome://resources/cr_elements/icons.html">
 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/app-layout/app-drawer/app-drawer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-flex-layout/iron-flex-layout.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-icon/iron-icon.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-header-panel/paper-header-panel.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-icon-button/paper-icon-button.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-input/paper-input.html">
 <link rel="import" href="/direction_delegate.html">
 <link rel="import" href="/i18n_setup.html">
@@ skipping 126 matching lines @@
         <paper-icon-button icon="cr:search" toggles></paper-icon-button>
         <paper-input id="search-input" label="$i18n{internalSearch}"
             no-label-float>
           <!-- TODO(dschuyler): implement internal search. -->
           <paper-icon-button suffix icon="cr:cancel">
           </paper-icon-button>
         </paper-input>
       </div>
     </div>
     <app-drawer swipe-open>
-      <!--TODO(dpapad): Restore waterfall effect or remove this TODO, depending
-        on outcome of crbug.com/621718-->
       <div class="drawer-header">$i18n{settings}</div>
       <div class="drawer-content">
         <settings-menu current-route="{{currentRoute}}" id="sideNav">
         </settings-menu>
       </div>
     </app-drawer>
     <paper-header-panel mode="waterfall">
       <settings-main prefs="{{prefs}}" current-route="{{currentRoute}}">
       </settings-main>
     </paper-header-panel>
   </template>
   <script src="settings_ui.js"></script>
 </dom-module>