Draw marker events on Timeline flame chart

Source/devtools/front_end/flameChart.css

 .overview-container {
     overflow: hidden;
     position: absolute;
     top: 0;
     width: 100%;
     height: 80px;
 }
 
 .chart-container {
     flex: auto;
@@ skipping 28 matching lines @@
     left: 10px;
     top: 25px;
     background-color: rgba(255, 255, 255, 0.8);
     pointer-events: none;
 }
 
 .chart-container .entry-info .title {
     font-weight: bold;
 }
 
+.flame-chart-marker-highlight-element {
+    position: absolute;
+    top: 0;
+    height: 20px;
+    width: 4px;
+    margin: 0 -2px;
+    content: "";
+    display: block;
+}
+
 .flame-chart-highlight-element {
     background-color: black;
     position: absolute;
     opacity: 0.2;
     pointer-events: none;
 }
 
 .flame-chart-selected-element {
     position: absolute;
     pointer-events: none;
     border-color: rgb(56, 121, 217);
     border-width: 2px;
     border-style: solid;
     background-color: rgba(56, 121, 217, 0.2);
 }
 
 .flame-chart-v-scroll {
     flex: 0 0 14px;
     overflow-x: hidden;
 }
 
 body.platform-mac .flame-chart-v-scroll {
     position: absolute;
     width: 14px;
     top: 0;
     right: 0;
     bottom: 0;
 }