[DevTools] Add groups to device select.

Source/devtools/front_end/overrides.css

Index: Source/devtools/front_end/overrides.css
diff --git a/Source/devtools/front_end/overrides.css b/Source/devtools/front_end/overrides.css
index 5e7693ce08b1102232722f6515649d66b47cb108..5e52a802830d1c3ec13c5db785331d61f6b08c20 100644
--- a/Source/devtools/front_end/overrides.css
+++ b/Source/devtools/front_end/overrides.css
@@ -304,11 +304,14 @@ button.overrides-swap {
 }
 
 .overrides-splash-screen {
-    display: flex;
-    align-items: center;
+    display: block;
     padding: 3px 10px;
 }
 
+.overrides-splash-screen > button {
+    margin: -4px 0;
+}
+
 .overrides-reset-button {
     margin: 9px 0 0 17px;
 }