[cross browser fix] Webkit state update behavior

for some incredibly frustrating reason, firefox correctly runs `finishParsing` after `this.setState` after `onChange` fires, but webkit browsers run it before `onChange`, thus the state shenanigans

and for some even more incredibly bizarre reason, `requestAnimationFrame` works for every browser :dead_inside:

src/components/date_picker/super_date_picker/date_popover/absolute_tab.test.tsx

@@ -18,6 +18,12 @@ jest.mock('../../date_picker', () => ({
 }));
 
 describe('EuiAbsoluteTab', () => {
+  // mock requestAnimationFrame to fire immediately
+  const rafSpy = jest
+    .spyOn(window, 'requestAnimationFrame')
+    .mockImplementation((cb: Function) => cb());
+  afterAll(() => rafSpy.mockRestore());
+
   const props = {
     dateFormat: 'MMM D, YYYY @ HH:mm:ss.SSS',
     timeFormat: 'HH:mm',

src/components/date_picker/super_date_picker/date_popover/absolute_tab.tsx

@@ -101,17 +101,19 @@ export class EuiAbsoluteTab extends Component<
 
   parseUserDateInput = (textInputValue: string) => {
     this.isParsing = true;
-    const finishParsing = () => {
+    // Wait a tick for state to finish updating (whatever gets returned),
+    // and then allow `onChange` user input to continue setting state
+    requestAnimationFrame(() => {
       this.isParsing = false;
-    };
+    });
 
     const invalidDateState = {
       textInputValue,
       isTextInvalid: true,
       valueAsMoment: null,
     };
     if (!textInputValue) {
-      return this.setState(invalidDateState, finishParsing);
+      return this.setState(invalidDateState);
     }
 
     const { onChange, dateFormat } = this.props;
@@ -128,17 +130,14 @@ export class EuiAbsoluteTab extends Component<
 
     if (dateIsValid) {
       onChange(valueAsMoment.toISOString());
-      this.setState(
-        {
-          textInputValue: valueAsMoment.format(this.props.dateFormat),
-          valueAsMoment: valueAsMoment,
-          hasUnparsedText: false,
-          isTextInvalid: false,
-        },
-        finishParsing
-      );
+      this.setState({
+        textInputValue: valueAsMoment.format(this.props.dateFormat),
+        valueAsMoment: valueAsMoment,
+        hasUnparsedText: false,
+        isTextInvalid: false,
+      });
     } else {
-      this.setState(invalidDateState, finishParsing);
+      this.setState(invalidDateState);
     }
   };