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

Source/devtools/front_end/network/RequestHeadersView.js

Index: Source/devtools/front_end/network/RequestHeadersView.js
diff --git a/Source/devtools/front_end/network/RequestHeadersView.js b/Source/devtools/front_end/network/RequestHeadersView.js
index 3dfe1398a292de30b4eee643f5c4fa2b34b43c25..042e3ff8ebfe8d302ee7f1fa83400abdb453d502 100644
--- a/Source/devtools/front_end/network/RequestHeadersView.js
+++ b/Source/devtools/front_end/network/RequestHeadersView.js
@@ -376,6 +376,8 @@ WebInspector.RequestHeadersView.prototype = {
 
     _refreshHTTPInformation: function()
     {
+        this.element.classList.toggle("cached", this._request.cached);
+
         var requestMethodElement = this._requestMethodTreeElement;
         requestMethodElement.hidden = !this._request.statusCode;
         var statusCodeElement = this._statusCodeTreeElement;
@@ -424,15 +426,17 @@ WebInspector.RequestHeadersView.prototype = {
      * @param {string} title
      * @param {!Array.<!WebInspector.NetworkRequest.NameValue>} headers
      * @param {!TreeElement} headersTreeElement
-     * @param {boolean=} showCaution
+     * @param {boolean=} provisionalHeaders
      */
-    _refreshHeaders: function(title, headers, headersTreeElement, showCaution)
+    _refreshHeaders: function(title, headers, headersTreeElement, provisionalHeaders)
     {
         headersTreeElement.removeChildren();
 
         var length = headers.length;
         this._refreshHeadersTitle(title, headersTreeElement, length);
 
+        var showCaution = provisionalHeaders && !this._request.cached;
+
         if (showCaution) {
             var cautionText = WebInspector.UIString("Provisional headers are shown");
             var cautionFragment = document.createDocumentFragment();