chrome/browser/resources/extensions/pack_extension_overlay.html

<div id="packExtensionOverlay" class="page">
  <h1 i18n-content="packExtensionOverlay"></h1>
  <div id="cbd-content-area" class="content-area">
    <div class="pack-extension-heading" i18n-content="packExtensionHeading">
    </div>
    <div class="pack-extension-text-boxes">
      <label i18n-content="packExtensionRootDir"></label>
      <input class="pack-extension-text-area" id="extensionRootDir" type="text">
      <button id="browseExtensionDir"
              i18n-content="packExtensionBrowseButton"></button>
    </div>
    <div class="pack-extension-text-boxes">
      <label i18n-content="packExtensionPrivateKey"></label>
      <input class="pack-extension-text-area"
             id="extensionPrivateKey" type="text">
      <button id="browsePrivateKey"
              i18n-content="packExtensionBrowseButton"></button>
    </div>
  </div>
  <div class="action-area">
    <div class="action-area-right">
      <div class="button-strip">
        <button id="packExtensionDismiss" i18n-content="cancel"></button>
        <button id="packExtensionCommit"
                i18n-content="packExtensionCommit"></button>
      </div>
    </div>
  </div>
</div>