DevTools: NetworkPanel: use optimistic JSON parser for response preview.

Source/devtools/front_end/network/RequestPreviewView.js

Index: Source/devtools/front_end/network/RequestPreviewView.js
diff --git a/Source/devtools/front_end/network/RequestPreviewView.js b/Source/devtools/front_end/network/RequestPreviewView.js
index 72818261f3ee956ff93b9f4cb47ddd99b86449f0..86819997269e121fa93d72c3f8dcafe7ce3957af 100644
--- a/Source/devtools/front_end/network/RequestPreviewView.js
+++ b/Source/devtools/front_end/network/RequestPreviewView.js
@@ -81,7 +81,10 @@ WebInspector.RequestPreviewView.prototype = {
      */
     _jsonView: function()
     {
-        var parsedJSON = WebInspector.RequestJSONView.parseJSON(this.request.content || "");
+        var request = this.request;
+        var content = request.content;
+        content = request.contentEncoded ? window.atob(content || "") : (content || "");
+        var parsedJSON = WebInspector.RequestJSONView.parseJSON(content);
         return parsedJSON ? new WebInspector.RequestJSONView(this.request, parsedJSON) : null;
     },