DevTools: Add dark theme hidden experiment

third_party/WebKit/Source/devtools/front_end/inspectorStyle.css

Index: third_party/WebKit/Source/devtools/front_end/inspectorStyle.css
diff --git a/third_party/WebKit/Source/devtools/front_end/inspectorStyle.css b/third_party/WebKit/Source/devtools/front_end/inspectorStyle.css
index 4beee86df446246dc6d5cec97a45f2bf0db94065..08a600627058978cce45df70ef97ee7bf3af450f 100644
--- a/third_party/WebKit/Source/devtools/front_end/inspectorStyle.css
+++ b/third_party/WebKit/Source/devtools/front_end/inspectorStyle.css
@@ -46,6 +46,10 @@ body {
     color: #222;
 }
 
+body.dark-theme {
+    -webkit-filter: invert(100%) hue-rotate(180deg) saturate(80%);
+}
+
 .platform-linux {
     color: rgb(48, 57, 66);
     font-family: Ubuntu, Arial, sans-serif;
@@ -554,6 +558,10 @@ body.inactive .sidebar-tree-item.selected {
     bottom: 0;
 }
 
+body.dark-theme .root-view {
+    background: white;
+}
+
 .viewport-control-gap-element {
     color: transparent;
 }