Text control elements should contain all (shadow DOM) children.

third_party/WebKit/LayoutTests/fast/forms/resources/common-spinbutton-click-in-iframe.js

 window.jsTestIsAsync = true;
 
 var iframe;
 var testInput;
 
 function getSpinButton(input)
 {
     if (!window.internals)
         return null;
     return getElementByPseudoId(internals.oldestShadowRoot(input), "-webkit-inner-spin-button");
@@ skipping 13 matching lines @@
         return;
     eventSender.mouseMoveTo(x, y);
 }
 
 function runIFrameLoaded(config)
 {
     testInput = iframe.contentDocument.getElementById('test');
     testInput.focus();
     var spinButton = getSpinButton(testInput);
     if (spinButton) {
+        var rect = spinButton.getBoundingClientRect();
         mouseMoveTo(
-            iframe.offsetLeft + spinButton.offsetLeft + spinButton.offsetWidth / 2,
-            iframe.offsetTop + spinButton.offsetTop + spinButton.offsetHeight / 4);
+            iframe.offsetLeft + rect.left + rect.width / 2,
+            iframe.offsetTop + rect.top + rect.height / 4);
     }
     mouseClick();
     shouldBeEqualToString('testInput.value', config['expectedValue']);
     iframe.parentNode.removeChild(iframe);
     finishJSTest();
 }
 
 function testClickSpinButtonInIFrame(config)
 {
     description('Checks mouse click on spin button in iframe.');
     if (!window.eventSender)
         debug('Please run in DumpRenderTree');
 
     iframe = document.createElement('iframe');
     iframe.addEventListener('load', function () { runIFrameLoaded(config) });
     iframe.srcdoc = '<input id=test type=' + config['inputType'] + ' value="' + config['initialValue'] + '">';
     document.body.appendChild(iframe);
 }