Add a command-line switch --enable-per-tile-painting.

webkit/glue/webpreferences.h

 // Copyright (c) 2011 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.
 //
 // A struct for managing webkit's settings.
 //
 // Adding new values to this class probably involves updating
 // WebKit::WebSettings, common/render_messages.cc, browser/tab_contents/
 // render_view_host_delegate_helper.cc, and browser/profiles/profile.cc.
 
@@ skipping 92 matching lines @@
   bool accelerated_plugins_enabled;
   bool memory_info_enabled;
   bool interactive_form_validation_enabled;
   bool fullscreen_enabled;
   bool allow_displaying_insecure_content;
   bool allow_running_insecure_content;
   bool should_print_backgrounds;
   bool enable_scroll_animator;
   bool hixie76_websocket_protocol_enabled;
   bool visual_word_movement_enabled;
+  bool per_tile_drawing_enabled;
   // We try to keep the default values the same as the default values in
   // chrome, except for the cases where it would require lots of extra work for
   // the embedder to use the same default value.
   WebPreferences();
   ~WebPreferences();
 
   void Apply(WebKit::WebView* web_view) const;
 };
 
 #endif  // WEBKIT_GLUE_WEBPREFERENCES_H__