Merge pull request #7722 from Rob--W/grab-to-pan-cssom-and-cleanup

Update to latest grab-to-pan version

web/grab_to_pan.js

@@ -142,7 +142,6 @@
       this.element.addEventListener('scroll', this._endPan, true);
       event.preventDefault();
       event.stopPropagation();
-      this.document.documentElement.classList.add(this.CSS_CLASS_GRABBING);
 
       var focusedElement = document.activeElement;
       if (focusedElement && !focusedElement.contains(event.target)) {
@@ -161,8 +160,18 @@
       }
       var xDiff = event.clientX - this.clientXStart;
       var yDiff = event.clientY - this.clientYStart;
-      this.element.scrollTop = this.scrollTopStart - yDiff;
-      this.element.scrollLeft = this.scrollLeftStart - xDiff;
+      var scrollTop = this.scrollTopStart - yDiff;
+      var scrollLeft = this.scrollLeftStart - xDiff;
+      if (this.element.scrollTo) {
+        this.element.scrollTo({
+          top: scrollTop,
+          left: scrollLeft,
+          behavior: 'instant',
+        });
+      } else {
+        this.element.scrollTop = scrollTop;
+        this.element.scrollLeft = scrollLeft;
+      }
       if (!this.overlay.parentNode) {
         document.body.appendChild(this.overlay);
       }