Add a command line flag (--enable-fixed-position-compositing) for enabling compositing

webkit/glue/webpreferences.cc

 // 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.
 
 #include "webkit/glue/webpreferences.h"
 
 #include <unicode/uchar.h>
 
 #include "base/string_util.h"
 #include "base/utf_string_conversions.h"
@@ skipping 61 matching lines @@
       privileged_webgl_extensions_enabled(false),
       show_composited_layer_borders(false),
       show_composited_layer_tree(false),
       show_fps_counter(false),
       asynchronous_spell_checking_enabled(true),
       accelerated_compositing_enabled(false),
       threaded_compositing_enabled(false),
       force_compositing_mode(false),
       allow_webui_compositing(false),
       composite_to_texture_enabled(false),
+      fixed_position_compositing_enabled(false),
       accelerated_layers_enabled(false),
       accelerated_video_enabled(false),
       accelerated_2d_canvas_enabled(false),
       accelerated_drawing_enabled(false),
       accelerated_plugins_enabled(false),
       memory_info_enabled(false),
       interactive_form_validation_enabled(true),
       fullscreen_enabled(false),
       allow_displaying_insecure_content(true),
       allow_running_insecure_content(false),
@@ skipping 165 matching lines @@
   settings->setAcceleratedCompositingEnabled(accelerated_compositing_enabled);
 
   settings->setUseThreadedCompositor(threaded_compositing_enabled);
 
   // Always enter compositing if requested on the command line.
   settings->setForceCompositingMode(force_compositing_mode);
 
   // Enable composite to offscreen texture if requested on the command line.
   settings->setCompositeToTextureEnabled(composite_to_texture_enabled);
 
+  // Enable compositing for fixed position elements if requested
+  // on the command line.
+  settings->setAcceleratedCompositingForFixedPositionEnabled(
+      fixed_position_compositing_enabled);
+
   // Enable gpu-accelerated 2d canvas if requested on the command line.
   settings->setAccelerated2dCanvasEnabled(accelerated_2d_canvas_enabled);
 
   // Enable gpu-accelerated drawing if requested on the command line.
   settings->setAcceleratedDrawingEnabled(accelerated_drawing_enabled);
 
   // Enabling accelerated layers from the command line enabled accelerated
   // 3D CSS, Video, and Animations.
   settings->setAcceleratedCompositingFor3DTransformsEnabled(
       accelerated_layers_enabled);
@@ skipping 31 matching lines @@
   settings->setFullScreenEnabled(fullscreen_enabled);
   settings->setAllowDisplayOfInsecureContent(allow_displaying_insecure_content);
   settings->setAllowRunningOfInsecureContent(allow_running_insecure_content);
   settings->setShouldPrintBackgrounds(should_print_backgrounds);
   settings->setEnableScrollAnimator(enable_scroll_animator);
   settings->setHixie76WebSocketProtocolEnabled(
       hixie76_websocket_protocol_enabled);
 
   WebNetworkStateNotifier::setOnLine(is_online);
 }