Make the position of 'n files selected' label synced with the width of navigation list.

ui/file_manager/file_manager/foreground/css/file_manager.css

Index: ui/file_manager/file_manager/foreground/css/file_manager.css
diff --git a/ui/file_manager/file_manager/foreground/css/file_manager.css b/ui/file_manager/file_manager/foreground/css/file_manager.css
index ef0c64fed9cea3c9f94974f108fa802068334e16..5f56732c2a779dbab92827edbfa0e27fcae9f941 100644
--- a/ui/file_manager/file_manager/foreground/css/file_manager.css
+++ b/ui/file_manager/file_manager/foreground/css/file_manager.css
@@ -368,14 +368,11 @@ body.selecting .dialog-header {
 #cloud-import-details div {
   border: 0px 0px 1px 0px solid gray;
   padding: 10px;
-};
+}
 
 #files-selected-label {
   display: none;
-  /* TODO(fukino): Move dynamically with the navigation area's separator. */
-  left: 252px;
-  position: absolute;
-  top: 18px;
+  margin: 0 10px;
 }
 
 body.selecting #files-selected-label {
@@ -387,6 +384,10 @@ body.selecting #files-selected-label {
   display: none
 }
 
+#cancel-selection-button-wrapper {
+  width: 240px;  /* initial value, same as .dialog-navigation-list's width. */
+}
+
 #cancel-selection-button > core-icon {
   -webkit-margin-end: 6px;
 }