[SP] Enable Slimming Paint by default in Chromium and Blink.

content/browser/renderer_host/render_view_host_impl.cc

Index: content/browser/renderer_host/render_view_host_impl.cc
diff --git a/content/browser/renderer_host/render_view_host_impl.cc b/content/browser/renderer_host/render_view_host_impl.cc
index a644758232d3cd3fbdc0e505abda4f07b94426a5..b3d221a5302bd16ae95c5b23c36c4d8d6ca0254b 100644
--- a/content/browser/renderer_host/render_view_host_impl.cc
+++ b/content/browser/renderer_host/render_view_host_impl.cc
@@ -468,8 +468,9 @@ WebPreferences RenderViewHostImpl::ComputeWebkitPrefs() {
   prefs.touch_adjustment_enabled =
       !command_line.HasSwitch(switches::kDisableTouchAdjustment);
 
-  prefs.slimming_paint_enabled =
-      command_line.HasSwitch(switches::kEnableSlimmingPaint);
+  prefs.slimming_paint_enabled = command_line.HasSwitch(
+      switches::kEnableSlimmingPaint) ||
+      !command_line.HasSwitch(switches::kDisableSlimmingPaint);
 
 #if defined(OS_MACOSX) || defined(OS_CHROMEOS)
   bool default_enable_scroll_animator = true;