DevTools: show HTTP headers of cached resources in network panel.

Source/devtools/front_end/networkPanel.css

 /*
  * Copyright (C) 2006, 2007, 2008 Apple Inc.  All rights reserved.
  * Copyright (C) 2009 Anthony Ricaud <rik@webkit.org>
  *
  * 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 148 matching lines @@
     color: rgb(33%, 33%, 33%);
     display: inline-block;
     margin-right: 0.5em;
     font-weight: bold;
     vertical-align: top;
     white-space: pre-wrap;
 }
 
 .resource-headers-view .outline-disclosure .header-value {
     display: inline;
-    margin-right: 100px;
+    margin-right: 1em;
     white-space: pre-wrap;
     word-break: break-all;
     margin-top: 1px;
 }
 
 .resource-cookies-view {
     display: none;
     position: absolute;
     top: 0;
     right: 0;
@@ skipping 131 matching lines @@
 
 .panel.network .split-view {
     flex: auto;
     position: relative;
 }
 
 .network-filters-header {
     flex: 0 0 23px;
     padding-right: 4px;
 }