Close EuiComboBox options when the page scrolls

[chandlerprall]

Summary

Fixes #2099 by auto-closing the combo box's options popover on scroll events.

I modified the first combo box example to the following for this within a scrollable container

  render() {
    const { selectedOptions } = this.state;
    return (
      <div>
        <div style={{
          height: '200px',
          overflowY: 'scroll'
        }}>
          <div style={{height: '50px'}}/>
          <EuiComboBox
            placeholder="Select or create options"
            options={this.options}
            selectedOptions={selectedOptions}
            onChange={this.onChange}
            onCreateOption={this.onCreateOption}
            isClearable={true}
            data-test-subj="demoComboBox"
          />
          <div style={{height: '500px'}}/>
        </div>
      </div>
    );
  }

Checklist

• This was checked in mobile
• This was checked in IE11
  - [ ] This was checked in dark mode
  - [ ] Any props added have proper autodocs
  - [ ] Documentation examples were added
• A changelog entry exists and is marked appropriately
• This was checked for breaking changes and labeled appropriately
  - [ ] Jest tests were updated or added to match the most common scenarios
  - [ ] This was checked against keyboard-only and screenreader scenarios
  - [ ] This required updates to Framer X components

[cchaos]

Tested in Chrome 👍
Tested in Fireforx 🆗 There's a bit of a lag before it will disappear but it's better than the alternative.

[chandlerprall]

There's a bit of a lag before it will disappear but it's better than the alternative.

Happens occasionally in some browsers besides Firefox, unfortunately that's from the browsers not emitting scroll events quickly, which is done for performance reasons :-/

[thompsongl]

Tested in Firefox, Chrome, Safari, IE11, and Edge.

Saw the lag, also, but otherwise 👍

Looks like a snapshot needs updating. CL, too.