[Media Router] Use common media-router-header for MR UI.

chrome/browser/resources/media_router/elements/issue_banner/issue_banner.html

 <link rel="import" href="chrome://resources/polymer/v1_0/polymer/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="../media_router_header/media_router_header.html">
 <dom-module name="issue-banner">
   <link rel="import" type="css" href="../../media_router_common.css">
   <link rel="import" type="css" href="issue_banner.css">
   <template>
-    <media-router-header id="issue-header"
-        view="[[currentView_]]" heading-text="[[headerText_]]"
-        hidden$="[[computeIsBlockingIssueHidden_(issue)]]">
-    </media-router-header>
     <div class$="[[computeIssueClass_(issue)]]">
       <div>
         <div hidden$="[[computeIsBlockingIssueHidden_(issue)]]">
           <iron-icon icon="error-outline" id="blocking-icon">
           </iron-icon>
         </div>
         <div id="title">[[issue.title]]</div>
       </div>
       <div id="buttons">
         <paper-button flat id="opt-button" class="button"
             on-click="onClickOptAction_"
             hidden$="[[computeOptionalActionHidden_(issue)]]">
           <span>[[secondaryActionButtonText_]]</span>
         </paper-button>
         <paper-button flat id="default-button"
             class="button action" on-click="onClickDefaultAction_">
           <span>[[defaultActionButtonText_]]</span>
         </paper-button>
       </div>
     </div>
   </template>
 <script src="issue_banner.js"></script>
 </dom-module>