Restrict size of image and video thumbnails

res/css/views/messages/_MVideoBody.scss

@@ -17,7 +17,7 @@ limitations under the License.
 span.mx_MVideoBody {
     video.mx_MVideoBody {
         max-width: 100%;
-        height: auto;
+        max-height: 300px;
         border-radius: 4px;
     }
 }

src/components/views/messages/MImageBody.js

@@ -362,7 +362,7 @@ export default class MImageBody extends React.Component {
         }
 
         // The maximum height of the thumbnail as it is rendered as an <img>
-        const maxHeight = Math.min(this.props.maxImageHeight || 600, infoHeight);
+        const maxHeight = Math.min(this.props.maxImageHeight || 240, infoHeight);
         // The maximum width of the thumbnail, as dictated by its natural
         // maximum height.
         const maxWidth = infoWidth * maxHeight / infoHeight;