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

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 963197ea7ec98e641732f3c1b9ddf9914471abd6..00c3718b11cddbb4a06df058d8c71f5915595b31 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -5699,7 +5699,7 @@ class SeqAsciiString: public SeqString {
   static const int kAlignedSize = POINTER_SIZE_ALIGN(kHeaderSize);
 
   // Maximal memory usage for a single sequential ASCII string.
-  static const int kMaxSize = 512 * MB;
+  static const int kMaxSize = 512 * MB - 1;
   // Maximal length of a single sequential ASCII string.
   // Q.v. String::kMaxLength which is the maximal size of concatenated strings.
   static const int kMaxLength = (kMaxSize - kHeaderSize);
@@ -5753,7 +5753,7 @@ class SeqTwoByteString: public SeqString {
   static const int kAlignedSize = POINTER_SIZE_ALIGN(kHeaderSize);
 
   // Maximal memory usage for a single sequential two-byte string.
-  static const int kMaxSize = 512 * MB;
+  static const int kMaxSize = 512 * MB - 1;
   // Maximal length of a single sequential two-byte string.
   // Q.v. String::kMaxLength which is the maximal size of concatenated strings.
   static const int kMaxLength = (kMaxSize - kHeaderSize) / sizeof(uint16_t);