chrome/browser/resources/pdf/elements/viewer-zoom-toolbar.html

    <style include="cr-hidden-style">
      :host {
        --button-position-offset: 48px;
        bottom: 0;
        padding: 48px 0;
        position: fixed;
        right: 0;
        user-select: none;
        z-index: 3;
      }

      :host-context([is-print-preview]) {
        --button-position-offset: 24px;
      }

      :host-context([is-print-preview][dir='ltr']),
      :host-context([dir='rtl']) {
        left: 0;
        right: auto;
      }

      :host-context([is-print-preview][dir='rtl']) {
        left: auto;
        right: 0;
      }

      #zoom-buttons {
        position: relative;
        right: var(--button-position-offset);
      }

      :host-context([is-print-preview][dir='ltr']) #zoom-buttons,
      :host-context([dir='rtl']) #zoom-buttons {
        left: var(--button-position-offset);
        right: auto;
      }

      :host-context([is-print-preview][dir='rtl']) #zoom-buttons {
        left: auto;
        right: var(--button-position-offset);
      }

      viewer-zoom-button {
        display: block;
      }

      /*
       * A larger gap between the fit button and the two-up view button
       * and above the bottom two zoom buttons.
       */
      #two-up-view-button,
      #zoom-in-button {
        margin-top: 24px;
      }

      /* A small gap between the zoom in/zoom out buttons. */
      #zoom-out-button {
        margin-top: 10px;
      }
    </style>
    <div id="zoom-buttons">
      <viewer-zoom-button id="fit-button" on-fabclick="fitToggle"
          delay="[[fitButtonDelay_]]"
          keyboard-navigation-active="[[keyboardNavigationActive_]]"
          icons="pdf:fullscreen-exit cr:fullscreen">
      </viewer-zoom-button>
      <!-- TODO(crbug.com/51472): Change icons for two-up-view-button -->
      <!-- once they are finalized. -->
      <viewer-zoom-button id="two-up-view-button" delay="100"
          disabled="[[annotationMode]]" hidden$="[[!twoUpViewEnabled]]"
          on-fabclick="twoUpViewToggle_"
          keyboard-navigation-active="[[keyboardNavigationActive_]]"
          icons="pdf:create pdf:eraser"></viewer-zoom-button>
      <viewer-zoom-button id="zoom-in-button" icons="pdf:add"
          keyboard-navigation-active="[[keyboardNavigationActive_]]"
          on-fabclick="zoomIn" delay="50"></viewer-zoom-button>
      <viewer-zoom-button id="zoom-out-button" icons="pdf:remove"
          keyboard-navigation-active="[[keyboardNavigationActive_]]"
          on-fabclick="zoomOut" delay="0"></viewer-zoom-button>
    </div>