docs: function () {
              var style,
                  px,
                  testSize = 10000,
                  div = document.createElement('div');
              div.style.display = 'block';
              div.style.position = 'absolute';
              div.style.width = testSize + 'pt';
              document.body.appendChild(div);
              style = util.getComputedStyle(div);
              if (style && style.width) {
                  px = parseFloat(style.width) / testSize;
              } else {
                  // @NOTE: there is a bug in Firefox where `getComputedStyle()`
                  // returns null if called in a hidden (`display:none`) iframe
                  // (https://bugzilla.mozilla.org/show_bug.cgi?id=548397), so we
                  // fallback to a default value if this happens.
                  px = DEFAULT_PT2PX_RATIO;
              }
              document.body.removeChild(div);
              return px;
          }