separate projectChanged, MenuBar doesn't need it to render

Rendering the MenuBar does not depend on projectChanged. Some of its
event handling does. Abstracting that dependency we can handle some
behaviour in MenuBar without extra renders.

src/components/menu-bar/confirm-replace-hoc.jsx

+import {connect} from 'react-redux';
+import PropTypes from 'prop-types';
+import bindAll from 'lodash.bindall';
+import React from 'react';
+
+const ConfirmReplaceHOC = function (WrappedComponent) {
+    class ConfirmReplaceProject extends React.PureComponent {
+        constructor (props) {
+            super(props);
+
+            bindAll(this, [
+                'confirmReadyToReplaceProject'
+            ]);
+        }
+
+        confirmReadyToReplaceProject (message) {
+            let readyToReplaceProject = true;
+            if (this.props.projectChanged && !this.props.canCreateNew) {
+                readyToReplaceProject = confirm(message); // eslint-disable-line no-alert
+            }
+            return readyToReplaceProject;
+        }
+
+        render () {
+            const {
+                /* eslint-disable no-unused-vars */
+                projectChanged,
+                /* eslint-enable no-unused-vars */
+                ...props
+            } = this.props;
+            return (<WrappedComponent
+                confirmReadyToReplaceProject={this.confirmReadyToReplaceProject}
+                {...props}
+            />);
+        }
+    }
+
+    ConfirmReplaceProject.propTypes = {
+        canCreateNew: PropTypes.bool,
+        projectChanged: PropTypes.bool
+    };
+
+    const _mapStateToProps = state => ({
+        projectChanged: state.scratchGui.projectChanged
+    });
+
+    return connect(_mapStateToProps)(ConfirmReplaceProject);
+};
+
+export default ConfirmReplaceHOC;

src/components/menu-bar/menu-bar.jsx

 import classNames from 'classnames';
 import {connect} from 'react-redux';
+import {compose} from 'redux';
 import {defineMessages, FormattedMessage, injectIntl, intlShape} from 'react-intl';
 import PropTypes from 'prop-types';
 import bindAll from 'lodash.bindall';
@@ -25,6 +26,7 @@ import LoginDropdown from './login-dropdown.jsx';
 import SB3Downloader from '../../containers/sb3-downloader.jsx';
 import DeletionRestorer from '../../containers/deletion-restorer.jsx';
 import TurboMode from '../../containers/turbo-mode.jsx';
+import ConfirmReplaceHOC from './confirm-replace-hoc.jsx';
 
 import {openTipsLibrary} from '../../reducers/modals';
 import {setPlayer} from '../../reducers/mode';
@@ -160,17 +162,14 @@ class MenuBar extends React.Component {
         document.removeEventListener('keydown', this.handleKeyPress);
     }
     handleClickNew () {
-        let readyToReplaceProject = true;
         // if the project is dirty, and user owns the project, we will autosave.
         // but if they are not logged in and can't save, user should consider
         // downloading or logging in first.
         // Note that if user is logged in and editing someone else's project,
         // they'll lose their work.
-        if (this.props.projectChanged && !this.props.canCreateNew) {
-            readyToReplaceProject = confirm( // eslint-disable-line no-alert
-                this.props.intl.formatMessage(sharedMessages.replaceProjectWarning)
-            );
-        }
+        const readyToReplaceProject = this.props.confirmReadyToReplaceProject(
+            this.props.intl.formatMessage(sharedMessages.replaceProjectWarning)
+        );
         this.props.onRequestCloseFile();
         if (readyToReplaceProject) {
             this.props.onClickNew(this.props.canSave && this.props.canCreateNew);
@@ -752,7 +751,6 @@ MenuBar.propTypes = {
     onShare: PropTypes.func,
     onToggleLoginOpen: PropTypes.func,
     onUpdateProjectTitle: PropTypes.func,
-    projectChanged: PropTypes.bool,
     projectTitle: PropTypes.string,
     renderLogin: PropTypes.func,
     sessionExists: PropTypes.bool,
@@ -776,7 +774,6 @@ const mapStateToProps = state => {
         isShowingProject: getIsShowingProject(loadingState),
         languageMenuOpen: languageMenuOpen(state),
         loginMenuOpen: loginMenuOpen(state),
-        projectChanged: state.scratchGui.projectChanged,
         projectTitle: state.scratchGui.projectTitle,
         sessionExists: state.session && typeof state.session.session !== 'undefined',
         username: user ? user.username : null
@@ -803,7 +800,11 @@ const mapDispatchToProps = dispatch => ({
     onSeeCommunity: () => dispatch(setPlayer(true))
 });
 
-export default injectIntl(connect(
-    mapStateToProps,
-    mapDispatchToProps
-)(MenuBar));
+export default compose(
+    injectIntl,
+    ConfirmReplaceHOC,
+    connect(
+        mapStateToProps,
+        mapDispatchToProps
+    )
+)(MenuBar);