DevTools: CssChecker: avoid selector crafting in AuditsPanel.

Source/devtools/front_end/audits/auditsPanel.css

Index: Source/devtools/front_end/audits/auditsPanel.css
diff --git a/Source/devtools/front_end/audits/auditsPanel.css b/Source/devtools/front_end/audits/auditsPanel.css
index bfb6d1f3350b5a8712d2addbdccb03cb8e642b4d..449ec4f2f9ff1866263b7e0265d70902f9cb88d8 100644
--- a/Source/devtools/front_end/audits/auditsPanel.css
+++ b/Source/devtools/front_end/audits/auditsPanel.css
@@ -121,9 +121,7 @@
     display: block;
 }
 
-.audit-result-view .severity-severe,
-.audit-result-view .severity-warning,
-.audit-result-view .severity-info {
+.audit-result-view .severity {
     background-image: url(Images/statusbarButtonGlyphs.png);
     background-size: 320px 144px;
     display: inline-block;
@@ -136,22 +134,20 @@
 }
 
 @media (-webkit-min-device-pixel-ratio: 1.5) {
-.audit-result-view .severity-severe,
-.audit-result-view .severity-warning,
-.audit-result-view .severity-info {
+.audit-result-view .severity {
     background-image: url(Images/statusbarButtonGlyphs_2x.png);
 }
 } /* media */
 
-.audit-result-view .severity-severe {
+.audit-result-view .severity.severe {
     background-position: -224px -96px;
 }
 
-.audit-result-view .severity-warning {
+.audit-result-view .severity.warning {
     background-position: -246px -96px;
 }
 
-.audit-result-view .severity-info {
+.audit-result-view .severity.info {
     background-position: -235px -96px;
 }