DevTools: NetworkPanel: Preview: do not try to show HTML as JSONP.

Source/devtools/front_end/network/RequestPreviewView.js

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 126 matching lines @@
             var htmlErrorPreview = this._htmlErrorPreview();
             if (htmlErrorPreview)
                 return htmlErrorPreview;
         }
 
         var xmlView = this._xmlView();
         if (xmlView)
             return xmlView;
 
         if (this.request.resourceType() === WebInspector.resourceTypes.XHR) {
-            var jsonView = this._jsonView();
-            if (jsonView)
-                return jsonView;
-            var htmlErrorPreview = this._htmlErrorPreview();
-            if (htmlErrorPreview)
-                return htmlErrorPreview;
+            var isHtml = false;
+            try {
+                isHtml = !!((new DOMParser()).parseFromString(this._requestContent(), mimeType)).body;
+            } catch (e) {
+            }
+            if (!isHtml) {
+                var jsonView = this._jsonView();
+                if (jsonView)
+                    return jsonView;
+            } else {
+                var htmlErrorPreview = this._htmlErrorPreview();
+                if (htmlErrorPreview)
+                    return htmlErrorPreview;
+            }
         }
 
         if (this._responseView.sourceView)
             return this._responseView.sourceView;
 
         if (this.request.resourceType() === WebInspector.resourceTypes.Other)
             return this._createEmptyView();
 
         return WebInspector.RequestView.nonSourceViewForRequest(this.request);
     },
 
     __proto__: WebInspector.RequestContentView.prototype
 }