Do deferred migration of maps after deoptimizing once.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index c0835e21eb9cb5d3df0d1f5ad1e464b6d4022323..db4c27e02f691615a2b6681ad44567bb6469ace4 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -5635,6 +5635,15 @@ class Map: public HeapObject {
   class IsUnstable:                 public BitField<bool, 29,  1> {};
   class IsMigrationTarget:          public BitField<bool, 30,  1> {};
 
+  // Bit field 4.
+  inline uint32_t bit_field4();
+  inline void set_bit_field4(uint32_t bits);
+
+  class HasMigrated:        public BitField<int,   0,  1> {};
+
+  inline void set_has_migrated(bool value);
+  inline bool has_migrated();
+
   // Tells whether the object in the prototype property will be used
   // for instances created from this function.  If the prototype
   // property is set to a value that is not a JSObject, the prototype
@@ -6185,7 +6194,8 @@ class Map: public HeapObject {
   static const int kCodeCacheOffset = kDescriptorsOffset + kPointerSize;
   static const int kDependentCodeOffset = kCodeCacheOffset + kPointerSize;
   static const int kBitField3Offset = kDependentCodeOffset + kPointerSize;
-  static const int kSize = kBitField3Offset + kPointerSize;
+  static const int kBitField4Offset = kBitField3Offset + kPointerSize;
+  static const int kSize = kBitField4Offset + kPointerSize;
 
   // Layout of pointer fields. Heap iteration code relies on them
   // being continuously allocated.