Fix notifications warning layout

For some reason, Chrome doesn't seem to make the central div in the
notifications warning wide enough, so it ends up wrapping. Fix this by making
the central div expand across the available space, instead of letting the
container for the close button do it.

Fixes https://github.com/vector-im/vector-web/issues/1687

src/components/views/globals/MatrixToolbar.js

@@ -35,7 +35,7 @@ module.exports = React.createClass({
         return (
             <div className="mx_MatrixToolbar">
                 <img className="mx_MatrixToolbar_warning" src="img/warning.svg" width="24" height="23" alt="/!\"/>
-                <div>
+                <div className="mx_MatrixToolbar_content">
                     You are not receiving desktop notifications. <a className="mx_MatrixToolbar_link" onClick={ this.onClick }>Enable them now</a>
                 </div>
                 <div className="mx_MatrixToolbar_close"><img src="img/cancel.svg" width="18" height="18" onClick={ this.hideToolbar } /></div>
@@ -43,4 +43,3 @@ module.exports = React.createClass({
         );
     }
 });
-

src/skins/vector/css/vector-web/views/globals/MatrixToolbar.css

@@ -33,6 +33,11 @@ limitations under the License.
     margin-top: -2px;
 }
 
+.mx_MatrixToolbar_content {
+    -webkit-flex: 1;
+    flex: 1;
+}
+
 .mx_MatrixToolbar_link
 {
     color: #fff ! important;
@@ -41,10 +46,7 @@ limitations under the License.
 }
 
 .mx_MatrixToolbar_close {
-    -webkit-flex: 1;
-    flex: 1;
     cursor: pointer;
-    text-align: right;
 }
 
 .mx_MatrixToolbar_close img {