[MD History] Create an icons.html for MD History.

ui/webui/resources/cr_elements/icons.html

 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-iconset-svg/iron-iconset-svg.html">
 
 <!--
 List commonly used icons here to prevent duplication.
 Do not add rarely used icons here; place those in your application.
 -->
 <iron-iconset-svg name="cr" size="24">
   <svg>
     <defs>
       <!--
       These icons are copied from Polymer's iron-icons and kept in sorted order.
       See http://goo.gl/Y1OdAq for instructions on adding additional icons.
       -->
       <g id="arrow-drop-down"><path d="M7 10l5 5 5-5z"></path></g>
       <g id="cancel"><path d="M12 2C6.47 2 2 6.47 2 12s4.47 10 10 10 10-4.47 10-10S17.53 2 12 2zm5 13.59L15.59 17 12 13.41 8.41 17 7 15.59 10.59 12 7 8.41 8.41 7 12 10.59 15.59 7 17 8.41 13.41 12 17 15.59z"></path></g>
 <if expr="chromeos">
       <g id="check"><path d="M9 16.17L4.83 12l-1.42 1.41L9 19 21 7l-1.41-1.41z"></path></g>
 </if>
+      <g id="chevron-left"><path d="M15.41 7.41L14 6l-6 6 6 6 1.41-1.41L10.83 12z"></path></g>

[tsergeant, 2016/05/25 06:49:53]

Actually, this should move into history/icons.html, since it's not used anywhere
else.

       <g id="chevron-right"><path d="M10 6L8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"></path></g>
       <g id="clear"><path d="M19 6.41L17.59 5 12 10.59 6.41 5 5 6.41 10.59 12 5 17.59 6.41 19 12 13.41 17.59 19 19 17.59 13.41 12z"></path></g>
       <g id="close"><path d="M19 6.41L17.59 5 12 10.59 6.41 5 5 6.41 10.59 12 5 17.59 6.41 19 12 13.41 17.59 19 19 17.59 13.41 12z"></path></g>
       <g id="domain"><path d="M12 7V3H2v18h20V7H12zM6 19H4v-2h2v2zm0-4H4v-2h2v2zm0-4H4V9h2v2zm0-4H4V5h2v2zm4 12H8v-2h2v2zm0-4H8v-2h2v2zm0-4H8V9h2v2zm0-4H8V5h2v2zm10 12h-8v-2h2v-2h-2v-2h2v-2h-2V9h8v10zm-2-8h-2v2h2v-2zm0 4h-2v2h2v-2z"></path></g>
       <g id="expand-less"><path d="M12 8l-6 6 1.41 1.41L12 10.83l4.59 4.58L18 14z"></path></g>
       <g id="expand-more"><path d="M16.59 8.59L12 13.17 7.41 8.59 6 10l6 6 6-6z"></path></g>
       <g id="extension"><path d="M20.5 11H19V7c0-1.1-.9-2-2-2h-4V3.5C13 2.12 11.88 1 10.5 1S8 2.12 8 3.5V5H4c-1.1 0-1.99.9-1.99 2v3.8H3.5c1.49 0 2.7 1.21 2.7 2.7s-1.21 2.7-2.7 2.7H2V20c0 1.1.9 2 2 2h3.8v-1.5c0-1.49 1.21-2.7 2.7-2.7 1.49 0 2.7 1.21 2.7 2.7V22H17c1.1 0 2-.9 2-2v-4h1.5c1.38 0 2.5-1.12 2.5-2.5S21.88 11 20.5 11z"></path></g>
       <g id="file-download"><path d="M19 9h-4V3H9v6H5l7 7 7-7zM5 18v2h14v-2H5z"></path></g>
       <g id="fullscreen"><path d="M7 14H5v5h5v-2H7v-3zm-2-4h2V7h3V5H5v5zm12 7h-3v2h5v-5h-2v3zM14 5v2h3v3h2V5h-5z"></path></g>
       <g id="group"><path d="M16 11c1.66 0 2.99-1.34 2.99-3S17.66 5 16 5c-1.66 0-3 1.34-3 3s1.34 3 3 3zm-8 0c1.66 0 2.99-1.34 2.99-3S9.66 5 8 5C6.34 5 5 6.34 5 8s1.34 3 3 3zm0 2c-2.33 0-7 1.17-7 3.5V19h14v-2.5c0-2.33-4.67-3.5-7-3.5zm8 0c-.29 0-.62.02-.97.05 1.16.84 1.97 1.97 1.97 3.45V19h6v-2.5c0-2.33-4.67-3.5-7-3.5z"></path></g>
       <g id="more-vert"><path d="M12 8c1.1 0 2-.9 2-2s-.9-2-2-2-2 .9-2 2 .9 2 2 2zm0 2c-1.1 0-2 .9-2 2s.9 2 2 2 2-.9 2-2-.9-2-2-2zm0 6c-1.1 0-2 .9-2 2s.9 2 2 2 2-.9 2-2-.9-2-2-2z"></path></g>
       <g id="person"><path d="M12 12c2.21 0 4-1.79 4-4s-1.79-4-4-4-4 1.79-4 4 1.79 4 4 4zm0 2c-2.67 0-8 1.34-8 4v2h16v-2c0-2.66-5.33-4-8-4z"></path></g>
       <g id="print"><path d="M19 8H5c-1.66 0-3 1.34-3 3v6h4v4h12v-4h4v-6c0-1.66-1.34-3-3-3zm-3 11H8v-5h8v5zm3-7c-.55 0-1-.45-1-1s.45-1 1-1 1 .45 1 1-.45 1-1 1zm-1-9H6v4h12V3z"></path></g>
       <g id="search"><path d="M15.5 14h-.79l-.28-.27C15.41 12.59 16 11.11 16 9.5 16 5.91 13.09 3 9.5 3S3 5.91 3 9.5 5.91 16 9.5 16c1.61 0 3.09-.59 4.23-1.57l.27.28v.79l5 4.99L20.49 19l-4.99-5zm-6 0C7.01 14 5 11.99 5 9.5S7.01 5 9.5 5 14 7.01 14 9.5 11.99 14 9.5 14z"></path></g>
       <g id="settings"><path d="M19.43 12.98c.04-.32.07-.64.07-.98s-.03-.66-.07-.98l2.11-1.65c.19-.15.24-.42.12-.64l-2-3.46c-.12-.22-.39-.3-.61-.22l-2.49 1c-.52-.4-1.08-.73-1.69-.98l-.38-2.65C14.46 2.18 14.25 2 14 2h-4c-.25 0-.46.18-.49.42l-.38 2.65c-.61.25-1.17.59-1.69.98l-2.49-1c-.23-.09-.49 0-.61.22l-2 3.46c-.13.22-.07.49.12.64l2.11 1.65c-.04.32-.07.65-.07.98s.03.66.07.98l-2.11 1.65c-.19.15-.24.42-.12.64l2 3.46c.12.22.39.3.61.22l2.49-1c.52.4 1.08.73 1.69.98l.38 2.65c.03.24.24.42.49.42h4c.25 0 .46-.18.49-.42l.38-2.65c.61-.25 1.17-.59 1.69-.98l2.49 1c.23.09.49 0 .61-.22l2-3.46c.12-.22.07-.49-.12-.64l-2.11-1.65zM12 15.5c-1.93 0-3.5-1.57-3.5-3.5s1.57-3.5 3.5-3.5 3.5 1.57 3.5 3.5-1.57 3.5-3.5 3.5z"></path></g>
       <g id="star"><path d="M12 17.27L18.18 21l-1.64-7.03L22 9.24l-7.19-.61L12 2 9.19 8.63 2 9.24l5.46 4.73L5.82 21z"></path></g>
       <g id="warning"><path d="M1 21h22L12 2 1 21zm12-3h-2v-2h2v2zm0-4h-2v-4h2v4z"></path></g>
 <if expr="chromeos">
       <g id="star-border"><path d="M22 9.24l-7.19-.62L12 2 9.19 8.63 2 9.24l5.46 4.73L5.82 21 12 17.27 18.18 21l-1.63-7.03L22 9.24zM12 15.4l-3.76 2.27 1-4.28-3.32-2.88 4.38-.38L12 6.1l1.71 4.04 4.38.38-3.32 2.88 1 4.28L12 15.4z"></path></g>
 </if>
     </defs>
   </svg>
 </iron-iconset-svg>