Add PaintOptimizations feature to control subsequence caching and empty phase skipping

content/child/runtime_features.cc

Index: content/child/runtime_features.cc
diff --git a/content/child/runtime_features.cc b/content/child/runtime_features.cc
index 29b72e11eeeed295ad7b83afa9de181f1077d00f..98c30c5bbf780dad1b3ac824b98139e230e07142 100644
--- a/content/child/runtime_features.cc
+++ b/content/child/runtime_features.cc
@@ -200,6 +200,9 @@ void SetRuntimeFeaturesDefaultsAndUpdateFromArgs(
         std::string("PointerEvent"), true);
   }
 
+  if (!base::FeatureList::IsEnabled(features::kPaintOptimizations))
+    WebRuntimeFeatures::enableFeatureFromString("PaintOptimizations", false);
+
   // Enable explicitly enabled features, and then disable explicitly disabled
   // ones.
   if (command_line.HasSwitch(switches::kEnableBlinkFeatures)) {