Create a common BaseDialog

I'm fed up with copying the boilerplate for modal dialogs the whole time.

src/components/views/dialogs/BaseDialog.js

@@ -0,0 +1,72 @@
+/*
+Copyright 2017 Vector Creations Ltd
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import React from 'react';
+
+import * as KeyCode from '../../../KeyCode';
+
+/**
+ * Basic container for modal dialogs.
+ *
+ * Includes a div for the title, and a keypress handler which cancels the
+ * dialog on escape.
+ */
+export default React.createClass({
+    displayName: 'BaseDialog',
+
+    propTypes: {
+        // onFinished callback to call when Escape is pressed
+        onFinished: React.PropTypes.func.isRequired,
+
+        // callback to call when Enter is pressed
+        onEnterPressed: React.PropTypes.func,
+
+        // CSS class to apply to dialog div
+        className: React.PropTypes.string,
+
+        // Title for the dialog.
+        // (could probably actually be something more complicated than a string if desired)
+        title: React.PropTypes.string.isRequired,
+
+        // children should be the content of the dialog
+        children: React.PropTypes.node,
+    },
+
+    _onKeyDown: function(e) {
+        if (e.keyCode === KeyCode.ESCAPE) {
+            e.stopPropagation();
+            e.preventDefault();
+            this.props.onFinished();
+        } else if (e.keyCode === KeyCode.ENTER) {
+            if (this.props.onEnterPressed) {
+                e.stopPropagation();
+                e.preventDefault();
+                this.props.onEnterPressed(e);
+            }
+        }
+    },
+
+    render: function() {
+        return (
+            <div onKeyDown={this._onKeyDown} className={this.props.className}>
+                <div className='mx_Dialog_title'>
+                    { this.props.title }
+                </div>
+                { this.props.children }
+            </div>
+        );
+    },
+});