Add feature for main frame before activation.

content/renderer/gpu/render_widget_compositor.cc

Index: content/renderer/gpu/render_widget_compositor.cc
diff --git a/content/renderer/gpu/render_widget_compositor.cc b/content/renderer/gpu/render_widget_compositor.cc
index 14123551506d1393fccccd8d23aecb706b3e9249..0aeb611d89446563f59e58f35fbe128d5843f66b 100644
--- a/content/renderer/gpu/render_widget_compositor.cc
+++ b/content/renderer/gpu/render_widget_compositor.cc
@@ -247,8 +247,7 @@ void RenderWidgetCompositor::Initialize(float device_scale_factor) {
     }
   }
   settings.main_frame_before_activation_enabled =
-      cmd->HasSwitch(cc::switches::kEnableMainFrameBeforeActivation) &&
-      !cmd->HasSwitch(cc::switches::kDisableMainFrameBeforeActivation);
+      cmd->HasSwitch(cc::switches::kEnableMainFrameBeforeActivation);
   settings.use_mouse_wheel_gestures = UseGestureBasedWheelScrolling();
 
   settings.default_tile_size = CalculateDefaultTileSize(device_scale_factor);