[InputEvent] Move 'beforeinput' logic into |CompositeEditCommand::willApplyEditing()| (3/3)

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

+<title>InputEvent order WRT 'compositionupdate'</title>
+<script src="../../../resources/testharness.js"></script>
+<script src="../../../resources/testharnessreport.js"></script>
+<p id="editable" contenteditable></p>
+<script>
+test(function() {
+    assert_not_equals(textInputController, undefined, 'This test requires textInputController.');
+
+    var eventOrderRecorder = [];
+    const editable = document.getElementById('editable');
+    ['beforeinput', 'input', 'compositionstart', 'compositionupdate', 'compositionend'].forEach(
+        eventType => document.addEventListener(eventType, function(event) {
+            eventOrderRecorder.push(`${eventType}:${event.inputType}-${event.data}-${editable.innerHTML}`);
+        })
+    );
+
+    editable.focus();
+    textInputController.setComposition("w");
+    textInputController.setComposition("wo");
+    textInputController.insertText("work");
+    console.log(eventOrderRecorder);
+    assert_array_equals(eventOrderRecorder,
+        ['compositionstart:undefined--',
+         'beforeinput:insertText-w-',
+         'compositionupdate:undefined-w-',
+         'input:insertText-w-w',
+         'beforeinput:insertText-wo-w',
+         'compositionupdate:undefined-wo-w',
+         'input:insertText-wo-wo',
+         'beforeinput:insertText-work-wo',
+         'compositionupdate:undefined-work-wo',
+         'input:insertText-work-work',
+         'compositionend:undefined-work-work']
+    );
+}, '"compositionupdate" should fire before "input" and after "beforeinput".');
+</script>