DevTools: Add a checkbox to enable async stacks in the sidebar header.

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 ac17edd49d90ac475315717c3783b4bf3cdbdd9d..84d9aab00ccade5494aad892ba3365e9d2eaab99 100644
--- a/Source/devtools/front_end/sidebarPane.css
+++ b/Source/devtools/front_end/sidebarPane.css
@@ -88,7 +88,6 @@
     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;
@@ -104,18 +103,15 @@
 }
 
 @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;
 }
@@ -134,11 +130,10 @@
     pointer-events: auto;
 }
 
-.sidebar-pane-toolbar > .pane-title-button {
+.sidebar-pane-toolbar > .pane-title-button,
+.sidebar-pane-toolbar > label {
     float: right;
-    width: 23px;
     height: 17px;
-    color: transparent;
     background-color: transparent;
     border: none;
     background-repeat: no-repeat;
@@ -148,6 +143,11 @@
     -webkit-appearance: none;
 }
 
+.sidebar-pane-toolbar > .pane-title-button {
+    width: 23px;
+    color: transparent;
+}
+
 .sidebar-pane-toolbar > .pane-title-button:hover {
     background-position: -23px 0;
 }
@@ -169,6 +169,14 @@
     background-image: url(Images/paneRefreshButtons.png);
 }
 
+.sidebar-pane-toolbar > label > input {
+    vertical-align: -2px;
+}
+
+.sidebar-pane-toolbar > label.scripts-callstack-async {
+    margin-right: 5px;
+}
+
 .sidebar-pane-subtitle {
     position: absolute;
     right: 0;