Re-land "Improve support for :read-only and :read-write pseudoclasses".

LayoutTests/fast/forms/resources/textarea-live-pseudo-selectors.js

 description("This test performs a check that :valid/:invalid CSS psudo selectors are lively applied.");
 
 // Setup for static elements.
 var form = document.createElement('form');
 document.body.appendChild(form);
 var nonForm = document.createElement('div');
 document.body.appendChild(nonForm);
 
 function makeInvalid() {
     var i = document.createElement('textarea');
     i.name = 'foo';
     i.required = true;
     i.value = '';
     form.appendChild(i);
     return i;
 }
 
 function backgroundOf(el) {
     return document.defaultView.getComputedStyle(el, null).getPropertyValue('background-color');
 }
 
 var elBackground = 'backgroundOf(el)';
 var invalidColor = 'rgb(255, 0, 0)';
 var normalColor = 'rgb(255, 255, 255)';
 var disabledColor = 'rgb(0, 0, 0)';
-var readOnlyColor = 'rgb(0, 255, 0)'
+var readOnlyColor = 'rgb(0, 255, 0)';
 var validColor = 'rgb(0, 0, 255)';
 
 // --------------------------------
 //     willValidate change
 // --------------------------------
 var el = makeInvalid();
 // Confirm this element is invalid.
 debug('Chheck the initial state:');
 shouldBe(elBackground, 'invalidColor');
 
@@ skipping 57 matching lines @@
 el.value = '1234567890';
 shouldBe(elBackground, 'validColor');
 // Make the value dirty by deleting the last character.
 el.focus();
 el.setSelectionRange(10, 10);
 document.execCommand('delete');
 el.maxLength = 5;
 shouldBe(elBackground, 'invalidColor');
 el.maxLength = 10;
 shouldBe(elBackground, 'validColor');