fix(input): fix placeholder text being read twice by screen readers (#10524)

Author: du6

src/components/input/input.js

@@ -339,8 +339,9 @@ function inputTextareaDirective($mdUtil, $window, $mdAria, $timeout, $mdGesture)
     var errorsSpacer = angular.element('<div class="md-errors-spacer">');
     element.after(errorsSpacer);
 
-    if (!containerCtrl.label) {
-      $mdAria.expect(element, 'aria-label', attr.placeholder);
+    var placeholderText = angular.isString(attr.placeholder) ? attr.placeholder.trim() : '';
+    if (!containerCtrl.label && !placeholderText.length) {
+      $mdAria.expect(element, 'aria-label');
     }
 
     element.addClass('md-input');

src/components/input/input.spec.js

@@ -477,7 +477,7 @@ describe('md-input-container directive', function() {
     expect(label.textContent).toEqual('bar');
   });
 
-  it('should put an aria-label on the input when no label is present', inject(function($timeout) {
+  it('should not copy placeholder text to aria-label on the input', inject(function($timeout) {
     var el = $compile(
       '<form name="form">' +
       '  <md-input-container md-no-float>' +
@@ -489,21 +489,9 @@ describe('md-input-container directive', function() {
     $timeout.flush();
 
     var input = el.find('input');
-    expect(input.attr('aria-label')).toBe('baz');
+    expect(input.attr('aria-label')).toBeUndefined();
   }));
 
-  it('should evaluate the placeholder expression before setting the aria-label', function() {
-    pageScope.placeholder = 'baz';
-    var el = $compile(
-      '<form name="form">' +
-      '  <md-input-container md-no-float>' +
-      '    <input placeholder="{{placeholder}}" ng-model="foo" name="foo">' +
-      '  </md-input-container>' +
-      '</form>')(pageScope);
-
-    expect(el.find('input').attr('aria-label')).toBe('baz');
-  });
-
   it('should put the container in "has value" state when input has a static value', function() {
     var scope = pageScope.$new();
     var template =