MD Downloads: move md_colors.css to useful place

chrome/browser/resources/md_downloads/manager.html

 <link rel="import" href="chrome://resources/html/cr.html">
 <link rel="import" href="chrome://resources/html/cr/ui.html">
 <link rel="import" href="chrome://resources/html/cr/ui/command.html">
 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/html/util.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-list/iron-list.html">
 <link rel="import" href="chrome://downloads/action_service.html">
 <link rel="import" href="chrome://downloads/constants.html">
 <link rel="import" href="chrome://downloads/i18n_setup.html">
 <link rel="import" href="chrome://downloads/item.html">
 <link rel="import" href="chrome://downloads/toolbar.html">
+<link rel="stylesheet" href="chrome://resources/css/md_colors.css">
 
 <dom-module id="downloads-manager">
   <template>
-    <link rel="stylesheet" href="chrome://resources/css/md_colors.css">
     <style no-process>
       #toolbar {
         background: var(--md-toolbar-color);
       }
     </style>
     <downloads-toolbar id="toolbar"></downloads-toolbar>
     <iron-list id="downloads-list" items="{{items_}}"
         hidden="[[!hasDownloads_]]">
       <template>
         <downloads-item data="[[item]]" hide-date="[[item.hideDate]]">
         </downloads-item>
       </template>
     </iron-list>
     <div id="no-downloads" hidden="[[hasDownloads_]]">
       <div>
         <div class="illustration"></div>
         <span><!-- Text populated dynamically. --></span>
       </div>
     </div>
   </template>
   <link rel="import" type="css" href="chrome://downloads/shared_style.css">
   <link rel="import" type="css" href="chrome://downloads/manager.css">
   <script src="chrome://downloads/manager.js"></script>
 </dom-module>