Revert "Remove unused component: SimpleRoomHeader"

This reverts commit eb50b4930f.

res/css/views/rooms/_RoomHeader.scss

@@ -84,6 +84,27 @@ limitations under the License.
     align-items: center;
 }
 
+.mx_RoomHeader_simpleHeader {
+    line-height: $font-52px;
+    color: $primary-content;
+    font-size: $font-18px;
+    font-weight: $font-semi-bold;
+    overflow: hidden;
+    margin-left: 63px;
+    text-overflow: ellipsis;
+    width: 100%;
+
+    .mx_RoomHeader_cancelButton {
+        float: right;
+    }
+
+    .mx_RoomHeader_icon {
+        margin-left: 14px;
+        margin-right: 24px;
+        vertical-align: -4px;
+    }
+}
+
 .mx_RoomHeader_name {
     flex: 0 1 auto;
     overflow: hidden;

src/components/views/rooms/SimpleRoomHeader.tsx

@@ -0,0 +1,53 @@
+/*
+Copyright 2016-2021 The Matrix.org Foundation C.I.C.
+
+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 { replaceableComponent } from "../../../utils/replaceableComponent";
+
+interface IProps {
+    title?: string;
+    // `src` to an image. Optional.
+    icon?: string;
+}
+
+/*
+ * A stripped-down room header used for things like the user settings
+ * and room directory.
+ */
+@replaceableComponent("views.rooms.SimpleRoomHeader")
+export default class SimpleRoomHeader extends React.PureComponent<IProps> {
+    public render(): JSX.Element {
+        let icon;
+        if (this.props.icon) {
+            icon = <img
+                className="mx_RoomHeader_icon"
+                src={this.props.icon}
+                width="25"
+                height="25"
+            />;
+        }
+
+        return (
+            <div className="mx_RoomHeader mx_RoomHeader_wrapper">
+                <div className="mx_RoomHeader_simpleHeader">
+                    { icon }
+                    { this.props.title }
+                </div>
+            </div>
+        );
+    }
+}