Implement select listbox using shadow DOM

LayoutTests/fast/scroll-behavior/resources/scroll-behavior-test.js

 // A ScrollBehaviorTest runs a set of ScrollBehaviorTestCases. The only
 // ScrollBehaviorTest method that should be called by external code is run().
 
 // Creates a ScrollBehaviorTest with arguments:
 // scrollElement - Element being scrolled.
 // scrollEventTarget - Target for scroll events for |scrollElement|.
 // testsCases - Array of ScrollBehaviorTestCases.
 // getEndPosition - Callback that takes a test case and start position, and
 //                  returns the corresponding end position (where positions
 //                  are dictionaries with x and y fields).
@@ skipping 29 matching lines @@
         this.scrollElement.scrollTop = {y: testCase.endY, behavior: "instant"};
         this.testCaseComplete();
     }
 };
 
 ScrollBehaviorTest.prototype.startNextTestCase = function() {
     if (this.currentTestCase >= this.testCases.length) {
         this.allTestCasesComplete();
         return;
     }
-
     var testCase = this.testCases[this.currentTestCase];
     var isSmoothTest = (testCase.js == "smooth" || (testCase.css == "smooth" && testCase.js != "instant"));
 
     this.asyncTest = async_test("Scroll x:" + testCase.x + ", y:" + testCase.y + ", smooth:" + isSmoothTest);
 
     var currentPosition = {};
     currentPosition.x = this.scrollElement.scrollLeft;
     currentPosition.y = this.scrollElement.scrollTop;
     var endPosition = this.getEndPosition(testCase, currentPosition);
     testCase.setStartPosition(currentPosition);
@@ skipping 64 matching lines @@
 
 ScrollBehaviorTestCase.prototype.setStartPosition = function(startPosition) {
     this.startX = startPosition.x;
     this.startY = startPosition.y;
 }
 
 ScrollBehaviorTestCase.prototype.setEndPosition = function(endPosition) {
     this.endX = endPosition.x;
     this.endY = endPosition.y;
 }