MD Downloads: fix some a11y issues

chrome/browser/resources/md_downloads/item.html

 <link rel="import" href="chrome://resources/html/action_link.html">
 <link rel="import" href="chrome://resources/html/cr.html">
 <link rel="import" href="chrome://resources/html/polymer.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-button/paper-button.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-icon-button/paper-icon-button-light.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-progress/paper-progress.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-styles/shadow.html">
 <link rel="import" href="chrome://downloads/action_service.html">
 <link rel="import" href="chrome://downloads/constants.html">
@@ skipping 12 matching lines @@
         display: none !important;
       }
 
       paper-button {
         font-weight: 500;
         margin: 0;
         min-width: auto;
       }
 
       #date {
-        color: rgb(104, 113, 116);
+        color: rgb(103, 112, 115);

[calamity, 2016/12/09 01:31:42]

Is this a remnant from the old blue-grey color days? Should we ask Alan if we
can just make this grey?

[Dan Beam, 2016/12/09 02:03:54]

talked with bettes@, says it's cool to use grey 700 here and in settings

         font-size: 100%;
         font-weight: 500;
         margin: 24px auto 10px;
         width: var(--downloads-card-width);
       }
 
       #date:empty {
         display: none;
       }
 
@@ skipping 103 matching lines @@
         color: inherit;
         margin-top: 6px;
         min-height: 0;
         overflow: hidden;
         text-decoration: none;
         text-overflow: ellipsis;
         white-space: nowrap;
       }
 
       .is-active #url {
-        color: #969696;
+        color: var(--paper-grey-600);
       }
 
       #progress,
       #description:not(:empty),
       .controls {
         margin-top: 16px;
       }
 
       .is-active #description {
         color: #616161;
@@ skipping 36 matching lines @@
       .is-active #controlled-by a {
         color: rgb(51, 103, 214);
       }
 
       #remove-wrapper {
         align-self: flex-start;
         margin: 0;
       }
 
       #remove {
-        color: #969696;
+        color: var(--paper-grey-600);
         font-size: 16px;
         height: 32px;
         line-height: 17px;  /* TODO(dbeam): why is this necesssary? */
         width: 32px;
       }
 
       #incognito {
         bottom: 20px;
         content: -webkit-image-set(
             url(chrome://downloads/1x/incognito_marker.png) 1x,
@@ skipping 86 matching lines @@
       </div>
 
       <div id="incognito" title="$i18n{inIncognito}" hidden="[[!data.otr]]">
       </div>
     </div>
 
   </template>
   <link rel="import" type="css" href="chrome://resources/css/action_link.css">
   <script src="chrome://downloads/item.js"></script>
 </dom-module>