[InputEvent] Allow transpose and yank in plain-text field

third_party/WebKit/LayoutTests/fast/events/inputevents/inputevent-yank.html

Index: third_party/WebKit/LayoutTests/fast/events/inputevents/inputevent-yank.html
diff --git a/third_party/WebKit/LayoutTests/fast/events/inputevents/inputevent-yank.html b/third_party/WebKit/LayoutTests/fast/events/inputevents/inputevent-yank.html
index dcc027b493c9fc5aed8eb2a55ec7caecc00c94c1..0a9fb6f164317d87a31b2210ceacc022a426f1cc 100644
--- a/third_party/WebKit/LayoutTests/fast/events/inputevents/inputevent-yank.html
+++ b/third_party/WebKit/LayoutTests/fast/events/inputevents/inputevent-yank.html
@@ -2,6 +2,7 @@
 <script src="../../../resources/testharness.js"></script>
 <script src="../../../resources/testharnessreport.js"></script>
 <div id="editable" contenteditable></div>
+<textarea id="txt"></textarea>
 <script>
 test(() => {
     assert_not_equals(window.eventSender, undefined, 'This test requires eventSender.');
@@ -30,5 +31,34 @@ test(() => {
     testRunner.execCommand('yank');
     assert_equals(editable.innerHTML, 'abc');
     assert_equals(eventRecorder, 'beforeinput-insertFromYank-abc-input-insertFromYank-abc-');
-});
+}, 'Yank on contenteditable');
+
+test(() => {
+    assert_not_equals(window.eventSender, undefined, 'This test requires eventSender.');
+    assert_not_equals(window.testRunner, undefined, 'This test requires testRunner.');
+
+    let eventRecorder = '';
+    document.addEventListener('beforeinput', event => {
+        eventRecorder += `beforeinput-${event.inputType}-${event.data}-`;
+    });
+    document.addEventListener('input', event => {
+        eventRecorder += `input-${event.inputType}-${event.data}-`;
+    });
+
+    const txt = document.getElementById('txt');
+    txt.value = 'abc';
+    txt.focus();
+    txt.setSelectionRange(3, 3); // End of first line.
+
+    // Delete a word to setup kill buffer.
+    eventSender.keyDown('Backspace', ['altKey']);
+    assert_equals(txt.value, '');
+
+    // Test Yank.
+    testRunner.execCommand('undo'); // Execute undo to close last typing command.
+    eventRecorder = '';
+    testRunner.execCommand('yank');
+    assert_equals(txt.value, 'abc');
+    assert_equals(eventRecorder, 'beforeinput-insertFromYank-abc-input-insertFromYank-abc-');
+}, 'Yank on <textarea>');
 </script>