chrome/browser/resources/extensions/pack_extension_overlay.html

<div id="pack-extension-overlay" class="page">
  <div class="close-button"></div>
  <h1>$i18n{packExtensionOverlay}</h1>
  <div id="cbd-content-area" class="content-area">
    <div class="pack-extension-heading">$i18n{packExtensionHeading}</div>
    <div class="pack-extension-text-boxes">
      <label for="extension-root-dir">$i18n{packExtensionRootDir}</label>
      <input class="pack-extension-text-area" id="extension-root-dir"
          type="text">
      <button id="browse-extension-dir">
        $i18n{packExtensionBrowseButton}
      </button>
    </div>
    <div class="pack-extension-text-boxes">
      <label for="extension-private-key">$i18n{packExtensionPrivateKey}</label>
      <input class="pack-extension-text-area" id="extension-private-key"
          type="text">
      <button id="browse-private-key">
        $i18n{packExtensionBrowseButton}
      </button>
    </div>
  </div>
  <div class="action-area">
    <div class="action-area-right">
      <div class="button-strip">
        <button id="pack-extension-dismiss">$i18n{cancel}</button>
        <button id="pack-extension-commit">
          $i18n{packExtensionCommit}
        </button>
      </div>
    </div>
  </div>
</div>