DevTools: Show asynchronous call stacks on frontend.

Source/devtools/front_end/sidebarPane.css

Index: Source/devtools/front_end/sidebarPane.css
diff --git a/Source/devtools/front_end/sidebarPane.css b/Source/devtools/front_end/sidebarPane.css
index 4f666bce7b7e1d2b413125fc1ddd3011de98b727..ac17edd49d90ac475315717c3783b4bf3cdbdd9d 100644
--- a/Source/devtools/front_end/sidebarPane.css
+++ b/Source/devtools/front_end/sidebarPane.css
@@ -88,6 +88,7 @@
     border-bottom: 1px solid rgb(178, 178, 178);
 }
 
+.placard-group::before,
 .sidebar-pane-title::before {
     background-image: url(Images/statusbarButtonGlyphs.png);
     background-size: 320px 120px;
@@ -103,15 +104,18 @@
 }
 
 @media (-webkit-min-device-pixel-ratio: 1.5) {
+.placard-group::before,
 .sidebar-pane-title::before {
     background-image: url(Images/statusbarButtonGlyphs2x.png);
 }
 } /* media */
 
+.placard-group::before,
 .sidebar-pane-title::before {
     background-position: -4px -96px;
 }
 
+.placard-group.expanded::before,
 .sidebar-pane-title.expanded::before {
     background-position: -20px -96px;
 }