Add PaintOptimizations feature to control subsequence caching and empty phase skipping

content/public/common/content_features.cc

Index: content/public/common/content_features.cc
diff --git a/content/public/common/content_features.cc b/content/public/common/content_features.cc
index 95fc49d7354f4191699cbc8450d0900fa661ac1f..25b35ae569e55c0c1d7f65c8c6676d852a4278e3 100644
--- a/content/public/common/content_features.cc
+++ b/content/public/common/content_features.cc
@@ -69,6 +69,10 @@ const base::Feature kOptimizeIPCForSmallResource{
 const base::Feature kOriginTrials{"OriginTrials",
                                   base::FEATURE_ENABLED_BY_DEFAULT};
 
+// Paint optimizations including subsequence caching and empty phase skipping.
+const base::Feature kPaintOptimizations{"PaintOptimizations",
+                                        base::FEATURE_ENABLED_BY_DEFAULT};
+
 // Partial support for pointer event feature.
 const base::Feature kPointerEvents{"PointerEvent",
                                    base::FEATURE_DISABLED_BY_DEFAULT};