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

content/shell/renderer/layout_test/blink_test_runner.cc

Index: content/shell/renderer/layout_test/blink_test_runner.cc
diff --git a/content/shell/renderer/layout_test/blink_test_runner.cc b/content/shell/renderer/layout_test/blink_test_runner.cc
index ebba1156ae0383f3dde3da1a26788584a4c5b199..e36382c71b2dfd0fe92eb7c0052fca3bee37e6a7 100644
--- a/content/shell/renderer/layout_test/blink_test_runner.cc
+++ b/content/shell/renderer/layout_test/blink_test_runner.cc
@@ -797,7 +797,9 @@ void BlinkTestRunner::CaptureDump() {
   }
 
   if (base::CommandLine::ForCurrentProcess()->HasSwitch(
-          switches::kEnableSlimmingPaint)) {
+          switches::kEnableSlimmingPaint) ||
+      !base::CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kDisableSlimmingPaint)) {
       // Force a layout/paint by the end of the test to ensure test coverage of
       // incremental painting in slimming paint mode.
       proxy()->LayoutAndPaintAsyncThen(base::Bind(