MD Settings: Allow copying text to clipboard from the About page.

chrome/browser/resources/settings/about_page/detailed_build_info.html

 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="/about_page/about_page_browser_proxy.html">
 <link rel="import" href="/about_page/channel_switcher_dialog.html">
 <link rel="import" href="/i18n_setup.html"
 <link rel="import" href="/settings_shared_css.html">
 <link rel="import" href="chrome://resources/cr_elements/icons.html">
 <link rel="import" href="chrome://resources/html/i18n_behavior.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">
 
 <dom-module id="settings-detailed-build-info">
   <template>
-    <style include="settings-shared"></style>
+    <style include="settings-shared">
+      .secondary {
+        -webkit-user-select: text;
+      }
+    </style>
     <div class="settings-box two-line">
       <div class="start">
         <!-- TODO(dpapad): Localize string -->
         <div>Platform</div>
         <div class="secondary" id="osVersion">[[versionInfo_.osVersion]]</div>
       </div>
     </div>
     <div class="settings-box two-line"
         hidden$="[[!shouldShowVersion_(versionInfo_.osFirmware)]]">
       <div class="start">
@@ skipping 57 matching lines @@
     <div class="settings-box two-line">
       <div class="start">
         <!-- TODO(dpapad): Localize string -->
         <div>Build date</div>
         <div class="secondary">$i18n{aboutBuildDate}</div>
       </div>
     </div>
   </template>
   <script src="detailed_build_info.js"></script>
 </dom-module>