fix ie9/10 bounding top bug

src/utils/popper.js

@@ -1148,13 +1148,22 @@
      */
     function getBoundingClientRect(element) {
         var rect = element.getBoundingClientRect();
+
+        // whether the IE version is lower than 11
+        var isIE = navigator.userAgent.indexOf("MSIE") != -1;
+
+        // fix ie document bouding top always 0 bug
+        var rectTop = isIE && element.tagName === 'HTML'
+            ? -element.scrollTop
+            : rect.top;
+
         return {
             left: rect.left,
-            top: rect.top,
+            top: rectTop,
             right: rect.right,
             bottom: rect.bottom,
             width: rect.right - rect.left,
-            height: rect.bottom - rect.top
+            height: rect.bottom - rectTop
         };
     }