[DevTools] Group options in network presets select.

Source/devtools/front_end/ui/helpScreen.css

 .help-window-outer {
     position: absolute !important;
     top: 0;
     left: 0;
     right: 0;
     bottom: 0;
     z-index: 2000;
 }
 
 .help-window-main {
@@ skipping 540 matching lines @@
     display: none;
 }
 
 .settings-experiment-hidden label {
     background-color: #ddd;
 }
 
 .settings-developer-mode .settings-experiment-hidden {
     display: block;
 }
+
+.highlighted-setting {
+    animation: highlight-animation 5s linear;
+    animation-iteration-count: 1;
+}
+
+@keyframes highlight-animation {
+    0% { outline: auto 3px transparent; }
+    20% { outline: auto 3px rgb(255, 156, 0); }
+    80% { outline: auto 3px rgb(255, 156, 0); }
+    100% { outline: auto 3px transparent; }
+}