Revert of cc: Remove the --enable-partial-swap flag.

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 de34efced45e6eb53fa7d5e98061dffe5590eb41..24519d8376957ec8f5804e516e8f11c7af59ef0a 100644
--- a/content/renderer/gpu/render_widget_compositor.cc
+++ b/content/renderer/gpu/render_widget_compositor.cc
@@ -170,7 +170,8 @@
         settings.top_controls_hide_threshold = hide_threshold;
   }
 
-  settings.partial_swap_enabled = widget->AllowPartialSwap();
+  settings.partial_swap_enabled = widget->AllowPartialSwap() &&
+      cmd->HasSwitch(cc::switches::kEnablePartialSwap);
   settings.background_color_instead_of_checkerboard =
       cmd->HasSwitch(cc::switches::kBackgroundColorInsteadOfCheckerboard);
   settings.show_overdraw_in_tracing =