Remove the classList polyfill

This is only relevant for browsers that we don't intend to support with PDF.js version `2.0`.

src/shared/compatibility.js

@@ -143,74 +143,6 @@ PDFJS.compatibilityChecked = true;
   });
 })();
 
-// HTMLElement classList property
-// Support: IE<10, Android<4.0, iOS<5.0
-(function checkClassListProperty() {
-  function changeList(element, itemName, add, remove) {
-    var s = element.className || '';
-    var list = s.split(/\s+/g);
-    if (list[0] === '') {
-      list.shift();
-    }
-    var index = list.indexOf(itemName);
-    if (index < 0 && add) {
-      list.push(itemName);
-    }
-    if (index >= 0 && remove) {
-      list.splice(index, 1);
-    }
-    element.className = list.join(' ');
-    return (index >= 0);
-  }
-
-  if (!hasDOM) {
-    return;
-  }
-
-  var div = document.createElement('div');
-  if ('classList' in div) {
-    return; // classList property exists
-  }
-
-  var classListPrototype = {
-    add(name) {
-      changeList(this.element, name, true, false);
-    },
-    contains(name) {
-      return changeList(this.element, name, false, false);
-    },
-    remove(name) {
-      changeList(this.element, name, false, true);
-    },
-    toggle(name) {
-      changeList(this.element, name, true, true);
-    },
-  };
-
-  Object.defineProperty(HTMLElement.prototype, 'classList', {
-    get() {
-      if (this._classList) {
-        return this._classList;
-      }
-
-      var classList = Object.create(classListPrototype, {
-        element: {
-          value: this,
-          writable: false,
-          enumerable: true,
-        },
-      });
-      Object.defineProperty(this, '_classList', {
-        value: classList,
-        writable: false,
-        enumerable: false,
-      });
-      return classList;
-    },
-    enumerable: true,
-  });
-})();
-
 // Check onclick compatibility in Opera
 // Support: Opera<15
 (function checkOnClickCompatibility() {