[heap] No leakage of objects-visiting.h outside of heap.

src/heap/mark-compact.cc

Index: src/heap/mark-compact.cc
diff --git a/src/heap/mark-compact.cc b/src/heap/mark-compact.cc
index ce8a13683e27b5b4599dffd167cd700f396ba57a..7757b2cef5adbf10559a02f29b297fd80559bde0 100644
--- a/src/heap/mark-compact.cc
+++ b/src/heap/mark-compact.cc
@@ -37,6 +37,11 @@ const char* Marking::kGreyBitPattern = "11";
 const char* Marking::kImpossibleBitPattern = "01";
 
 
+// The following has to hold in order for {Marking::MarkBitFrom} to not produce
+// invalid {kImpossibleBitPattern} in the marking bitmap by overlapping.
+STATIC_ASSERT(Heap::kMinObjectSizeInWords >= 2);
+
+
 // -------------------------------------------------------------------------
 // MarkCompactCollector