Merge 135131 - input.value="" should clear date/time input elements with partial values

LayoutTests/fast/forms/resources/multiple-fields-value-set-empty.js

 var input;
 var emptyText;
 
 function testSettingEmptyStringClearsSubFields(type) {
     description('Check if input.value="" clears an input with partially-specified value.');
 
     input = document.createElement('input');
     input.type = type;
     document.body.appendChild(input);
     input.focus();
     emptyText = getUserAgentShadowTextContent(input);
     if (!window.eventSender)
         debug('This test needs to be run on DRT/WTR.');
     else {
         debug('Empty text: ' + emptyText);
         shouldNotBe('eventSender.keyDown("upArrow"); getUserAgentShadowTextContent(input)', 'emptyText');
         shouldBe('input.value = ""; getUserAgentShadowTextContent(input)', 'emptyText');
         input.remove();
     }
 }