DevTools: migrate the closeButton icons over to UI.Icon

third_party/WebKit/Source/devtools/front_end/ui/closeButton.css

Index: third_party/WebKit/Source/devtools/front_end/ui/closeButton.css
diff --git a/third_party/WebKit/Source/devtools/front_end/ui/closeButton.css b/third_party/WebKit/Source/devtools/front_end/ui/closeButton.css
index 01e83e35ce79b9b88c64f10e74506c9ab8012654..2d6d99185c65ec1d18abbb6334c6e6db167cbb0b 100644
--- a/third_party/WebKit/Source/devtools/front_end/ui/closeButton.css
+++ b/third_party/WebKit/Source/devtools/front_end/ui/closeButton.css
@@ -4,42 +4,31 @@
  * found in the LICENSE file.
  */
 
-div {
-    background-image: url(Images/toolbarButtonGlyphs.png);
-    background-size: 352px 168px;
-}
-
-@media (-webkit-min-device-pixel-ratio: 1.1) {
-div {
-    background-image: url(Images/toolbarButtonGlyphs_2x.png);
-}
-} /* media */
-
 .close-button {
     width: 14px;
     height: 14px;
-    background-position: -128px -96px;
     cursor: default;
+    display: flex;
+    align-items: center;
+    justify-content: center;
 }
 
-.close-button:hover {
-    background-position: -96px -96px;
+.hover-icon, .active-icon {
+    display: none;
 }
 
-.close-button:active {
-    background-position: -111px -96px;
+.close-button:hover .default-icon, .close-button:active .default-icon {
+    display: none;
 }
 
-.close-button-gray {
-    width: 13px;
-    height: 13px;
-    background-position: -175px -96px;
+.close-button:hover .hover-icon {
+    display: block;
 }
 
-.close-button-gray:hover {
-    background-position: -143px -96px;
+.close-button:active .hover-icon {
+    display: none !important;
 }
 
-.close-button-gray:active {
-    background-position: -160px -96px;
+.close-button:active .active-icon {
+    display: block;
 }