Fix DnD jank...

chrome/browser/resources/new_new_tab.js

 
 // Helpers
 
 function $(id) {
   return document.getElementById(id);
 }
 
 // TODO(arv): Remove these when classList is available in HTML5.
 // https://bugs.webkit.org/show_bug.cgi?id=20709
 function hasClass(el, name) {
@@ skipping 1037 matching lines @@
 
 window.addEventListener('blur', hideAllMenus);
 window.addEventListener('keydown', function(e) {
   if (e.keyIdentifier == 'Alt' || e.keyIdentifier == 'Meta') {
     hideAllMenus();
   }
 }, true);
 
 // Tooltip for elements that have text that overflows.
 document.addEventListener('mouseover', function(e) {
+  // We don't want to do this while we are dragging because it makes things very
+  // janky
+  if (dnd.dragItem) {
+    return;
+  }
+
   var el = findAncestor(e.target, function(el) {
     return el.xtitle;
   });
   if (el && el.xtitle != el.title) {
     if (el.scrollWidth > el.clientWidth) {
       el.title = el.xtitle;
     } else {
       el.title = '';
     }
   }
@@ skipping 117 matching lines @@
     el.addEventListener('dragover', bind(this.handleDragOver, this));
     el.addEventListener('dragleave', bind(this.handleDragLeave, this));
     el.addEventListener('drop', bind(this.handleDrop, this));
     el.addEventListener('dragend', bind(this.handleDragEnd, this));
     el.addEventListener('drag', bind(this.handleDrag, this));
     el.addEventListener('mousedown', bind(this.handleMouseDown, this));
   }
 };
 
 dnd.init();