Merge pull request #3491 from plotly/3489-v-modebar-ie11-pr

replace prepend() calls since they aren't supported in IE11

Author: antoinerg

Diff for: src/components/modebar/modebar.js

@@ -88,7 +88,7 @@ proto.update = function(graphInfo, buttons) {
             }
 
             if(fullLayout.modebar.orientation === 'v') {
-                this.element.prepend(logoGroup);
+                this.element.insertBefore(logoGroup, this.element.childNodes[0]);
             } else {
                 this.element.appendChild(logoGroup);
             }

Diff for: test/jasmine/assets/unpolyfill.js

@@ -18,5 +18,17 @@
                 ].join(' '));
             }
         });
+
+        Object.defineProperty(item, 'prepend', {
+            configurable: true,
+            enumerable: true,
+            writable: true,
+            value: function remove() {
+                throw Error([
+                    'test/jasmine/assets/unpolyfill.js error: calling ChildNode.prepend()',
+                    'which is not available in IE.'
+                ].join(' '));
+            }
+        });
     });
 })([Element.prototype, CharacterData.prototype, DocumentType.prototype]);