Add UI for creating polls (#10184)

* Add actions and reducers for polls

* Add poll button

* Disable media upload if poll enabled

* Add poll form

* Make delete & redraft work with polls

app/javascript/mastodon/features/compose/components/poll_button.js

@@ -0,0 +1,55 @@
+import React from 'react';
+import IconButton from '../../../components/icon_button';
+import PropTypes from 'prop-types';
+import { defineMessages, injectIntl } from 'react-intl';
+
+const messages = defineMessages({
+  add_poll: { id: 'poll_button.add_poll', defaultMessage: 'Add a poll' },
+  remove_poll: { id: 'poll_button.remove_poll', defaultMessage: 'Remove poll' },
+});
+
+const iconStyle = {
+  height: null,
+  lineHeight: '27px',
+};
+
+export default
+@injectIntl
+class PollButton extends React.PureComponent {
+
+  static propTypes = {
+    disabled: PropTypes.bool,
+    unavailable: PropTypes.bool,
+    active: PropTypes.bool,
+    onClick: PropTypes.func.isRequired,
+    intl: PropTypes.object.isRequired,
+  };
+
+  handleClick = () => {
+    this.props.onClick();
+  }
+
+  render () {
+    const { intl, active, unavailable, disabled } = this.props;
+
+    if (unavailable) {
+      return null;
+    }
+
+    return (
+      <div className='compose-form__poll-button'>
+        <IconButton
+          icon='tasks'
+          title={intl.formatMessage(active ? messages.remove_poll : messages.add_poll)}
+          disabled={disabled}
+          onClick={this.handleClick}
+          className={`compose-form__poll-button-icon ${active ? 'active' : ''}`}
+          size={18}
+          inverted
+          style={iconStyle}
+        />
+      </div>
+    );
+  }
+
+}