DevTools: [Documentation] fix css styles for renderer

Source/devtools/front_end/documentation/DocumentationView.js

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /**
  * @constructor
  * @extends {WebInspector.View}
  */
 WebInspector.DocumentationView = function()
 {
@@ skipping 199 matching lines @@
 
         for (var i = 0; i < examples.length; ++i) {
             var example = section.createChild("div", "documentation-example");
             var exampleDescription = example.createChild("div", "documentation-example-description-section");
             if (examples[i].liveUrl) {
                 var liveUrl = exampleDescription.createChild("a", "documentation-example-link");
                 liveUrl.classList.add("documentation-box");
                 liveUrl.href = examples[i].liveUrl;
                 liveUrl.textContent = WebInspector.UIString("Example");
             }
-            exampleDescription.appendChild(this._renderBlock(examples[i].description));
+            if (examples[i].description)
+                exampleDescription.appendChild(this._renderBlock(examples[i].description));
             var code = example.createChild("div", "documentation-code");
             code.classList.add("source-code");
             code.textContent = examples[i].code;
             if (!examples[i].language)
                 continue;
             var syntaxHighlighter = new WebInspector.DOMSyntaxHighlighter(WebInspector.DocumentationView._languageToMimeType[examples[i].language.toLowerCase()], true);
             syntaxHighlighter.syntaxHighlightNode(code);
         }
     },
 
@@ skipping 109 matching lines @@
         function computeDescriptors(column)
         {
             var token = textEditor.tokenAtTextPosition(textSelection.startLine, column);
             if (!token)
                 return [];
             var tokenText = textEditor.line(textSelection.startLine).substring(token.startColumn, token.endColumn);
             return urlProvider.itemDescriptors(tokenText);
         }
     }
 }