Remove all usage of -webkit-*gradient inside blink

Source/devtools/front_end/cssNamedFlows.css

 /*
  * Copyright (C) 2012 Adobe Systems Incorporated. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1. Redistributions of source code must retain the above
  *    copyright notice, this list of conditions and the following
  *    disclaimer.
@@ skipping 14 matching lines @@
  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
  * OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 .css-named-flow-collections-view .split-view-sidebar {
     overflow-x: hidden;
 }
 
 .css-named-flow-collections-view .tabbed-pane-header {
-    background: -webkit-gradient(linear, 0% 0%, 0% 100%, from(rgb(236, 236, 236)), to(rgb(217, 217, 217)));
+    background: linear-gradient(to bottom, rgb(236, 236, 236), rgb(217, 217, 217));
 }
 
 .css-named-flow-collections-view .info {
     font-style: italic;
     font-size: 10px;
     margin-top: -5px;
     position: absolute;
     top: 50%;
     text-align: center;
     width: 100%;
@@ skipping 44 matching lines @@
     content: url(Images/regionFit.png);
 }
 
 .css-named-flow-collections-view .region-overset::before {
     content: url(Images/regionOverset.png);
 }
 
 .css-named-flow-collections-view .split-view-contents .named-flow-element {
     margin: 0 0 0 -24px;
 }