Improve New Tab Page load performance

chrome/browser/dom_ui/chrome_url_data_manager.h

 // Copyright (c) 2006-2008 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 BROWSER_DOM_UI_CHROME_URL_DATA_MANAGER_H__
 #define BROWSER_DOM_UI_CHROME_URL_DATA_MANAGER_H__
 
 #include <map>
 #include <string>
 
@@ skipping 41 matching lines @@
 
     // Return the mimetype that should be sent with this response, or empty
     // string to specify no mime type.
     virtual std::string GetMimeType(const std::string& path) const = 0;
 
     // Report that a request has resulted in the data |bytes|.
     // If the request can't be satisfied, pass NULL for |bytes| to indicate
     // the request is over.
     void SendResponse(int request_id, RefCountedBytes* bytes);
 
-    MessageLoop* message_loop() const { return message_loop_; }
+    // Returns the MessageLoop on which the DataSource wishes to have
+    // StartDataRequest called to handle the request for |path|.  If the
+    // DataSource does not care which thread StartDataRequest is called on,
+    // this should return NULL.  The default implementation always returns
+    // message_loop_, which generally results in processing on the UI thread.
+    // It may be beneficial to return NULL for requests that are safe to handle
+    // directly on the IO thread.  This can improve performance by satisfying
+    // such requests more rapidly when there is a large amount of UI thread
+    // contention.
+    virtual MessageLoop* MessageLoopForRequestPath(const std::string& path)
+        const;
+
     const std::string& source_name() const { return source_name_; }
 
     static void SetFontAndTextDirection(DictionaryValue* localized_strings);
 
    private:
     // The name of this source.
     // E.g., for favicons, this could be "favicon", which results in paths for
     // specific resources like "favicon/34" getting sent to this source.
     const std::string source_name_;
 
@@ skipping 77 matching lines @@
 extern ChromeURLDataManager chrome_url_data_manager;
 
 // Register our special URL handler under our special URL scheme.
 // Must be done once at startup.
 void RegisterURLRequestChromeJob();
 
 // Undoes the registration done by RegisterURLRequestChromeJob.
 void UnregisterURLRequestChromeJob();
 
 #endif  // BROWSER_DOM_UI_CHROME_URL_DATA_MANAGER_H__