Migrate instance of deprecated maps in HCheckMaps.

src/objects-inl.h

Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index d2aadabbcf95d3acdb6409e22f6d91be7b554346..ed266436f190d18637170c15226fa180cf314fe2 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -3617,6 +3617,17 @@ bool Map::is_deprecated() {
 }
 
 
+void Map::set_migration_target(bool value) {
+  set_bit_field3(IsMigrationTarget::update(bit_field3(), value));
+}
+
+
+bool Map::is_migration_target() {
+  if (!FLAG_track_fields) return false;
+  return IsMigrationTarget::decode(bit_field3());
+}
+
+
 void Map::freeze() {
   set_bit_field3(IsFrozen::update(bit_field3(), true));
 }
@@ -4215,7 +4226,20 @@ void Map::InitializeDescriptors(DescriptorArray* descriptors) {
 
 
 ACCESSORS(Map, instance_descriptors, DescriptorArray, kDescriptorsOffset)
-SMI_ACCESSORS(Map, bit_field3, kBitField3Offset)
+
+
+void Map::set_bit_field3(uint32_t bits) {
+  // Ensure the upper 2 bits have the same value by sign extending it. This is
+  // necessary to be able to use the 31st bit.
+  int value = bits << 1;
+  WRITE_FIELD(this, kBitField3Offset, Smi::FromInt(value >> 1));
+}
+
+
+uint32_t Map::bit_field3() {
+  Object* value = READ_FIELD(this, kBitField3Offset);
+  return Smi::cast(value)->value();
+}
 
 
 void Map::ClearTransitions(Heap* heap, WriteBarrierMode mode) {