Reland of "[heap] Divide available memory upon compaction tasks"

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 6c209b179207407623aa850d85587528c23b0a1c..e2d8e30678ff010f4c7a92a43b8477824639bf07 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -4408,6 +4408,11 @@ class FreeSpace: public HeapObject {
   static const int kSizeOffset = HeapObject::kHeaderSize;
   static const int kNextOffset = POINTER_SIZE_ALIGN(kSizeOffset + kPointerSize);
 
+  // Minimum size for any free space node. Required to be power of two.
+  static const int kMinSize = 32;
+  STATIC_ASSERT(kMinSize >= (kNextOffset + kPointerSize));
+  STATIC_ASSERT(IS_POWER_OF_TWO(kMinSize));
+
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(FreeSpace);
 };