Estimate a (close) upper bound on the size of black-marked objects on each page.

src/runtime.cc

Index: src/runtime.cc
diff --git a/src/runtime.cc b/src/runtime.cc
index b8888ba8544d4f7d63f60a54f9280b9b9053d6de..08573ffaabedbc480de613574a4ed69213f08db5 100644
--- a/src/runtime.cc
+++ b/src/runtime.cc
@@ -2819,6 +2819,9 @@ MUST_USE_RESULT static MaybeObject* StringReplaceRegExpWithEmptyString(
 
   Address end_of_string = answer->address() + string_size;
   isolate->heap()->CreateFillerObjectAt(end_of_string, delta);
+  if (Marking::IsBlack(Marking::MarkBitFrom(*answer))) {
+    MemoryChunk::IncrementLiveBytes(answer->address(), -delta);
+  }
 
   return *answer;
 }