Speculative fix for crash in DOMUIThumbnailSource.

chrome/browser/dom_ui/new_tab_ui.h

 // Copyright (c) 2010 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.
 
 #ifndef CHROME_BROWSER_DOM_UI_NEW_TAB_UI_H_
 #define CHROME_BROWSER_DOM_UI_NEW_TAB_UI_H_
 #pragma once
 
 #include <string>
 
@@ skipping 42 matching lines @@
   class NewTabHTMLSource : public ChromeURLDataManager::DataSource {
    public:
     explicit NewTabHTMLSource(Profile* profile);
 
     // Called when the network layer has requested a resource underneath
     // the path we registered.
     virtual void StartDataRequest(const std::string& path,
                                   bool is_off_the_record,
                                   int request_id);
 
-    virtual std::string GetMimeType(const std::string&) const {
-      return "text/html";
-    }
+    virtual std::string GetMimeType(const std::string&) const;
 
     // Setters and getters for first_run.
     static void set_first_run(bool first_run) { first_run_ = first_run; }
     static bool first_run() { return first_run_; }
 
    private:
-    ~NewTabHTMLSource() {}
+    virtual ~NewTabHTMLSource();
 
     // Whether this is the first run.
     static bool first_run_;
 
     // Pointer back to the original profile.
     Profile* profile_;
 
     DISALLOW_COPY_AND_ASSIGN(NewTabHTMLSource);
   };
 
@@ skipping 13 matching lines @@
 
   NotificationRegistrar registrar_;
 
   // The preference version. This used for migrating prefs of the NTP.
   static const int current_pref_version_ = 2;
 
   DISALLOW_COPY_AND_ASSIGN(NewTabUI);
 };
 
 #endif  // CHROME_BROWSER_DOM_UI_NEW_TAB_UI_H_