MD Bookmarks: Simplify and improve consistency of CSS

chrome/browser/resources/md_bookmarks/app.html

 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/html/cr/ui/splitter.html">
 <link rel="import" href="chrome://bookmarks/api_listener.html">
 <link rel="import" href="chrome://bookmarks/constants.html">
 <link rel="import" href="chrome://bookmarks/dnd_manager.html">
 <link rel="import" href="chrome://bookmarks/list.html">
 <link rel="import" href="chrome://bookmarks/router.html">
 <link rel="import" href="chrome://bookmarks/shared_vars.html">
 <link rel="import" href="chrome://bookmarks/store.html">
 <link rel="import" href="chrome://bookmarks/toolbar.html">
 <link rel="import" href="chrome://bookmarks/folder_node.html">
 <link rel="import" href="chrome://bookmarks/util.html">
 
 <dom-module id="bookmarks-app">
   <template>
     <style>
       :host {
+        color: var(--primary-text-color);
         display: flex;
         flex-direction: column;
         height: 100%;
+        line-height: 154%;  /* 20px. */
       }
 
       #main-container {
         display: flex;
         flex-direction: row;
         flex-grow: 1;
         overflow: auto;
       }
 
       #splitter {
@@ skipping 27 matching lines @@
        <div id="sidebar">
         <bookmarks-folder-node item-id="0" depth="-1"></bookmarks-folder-node>
       </div>
       <div id="splitter"></div>
       <bookmarks-list></bookmarks-list>
     </div>
     <bookmarks-router></bookmarks-router>
   </template>
   <script src="chrome://bookmarks/app.js"></script>
 </dom-module>