Make instance_size immediately useful for all fixed size objects.

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index 8359aa33529aed900efafe6391099a0568be8067..87a7efd4940210d30be68cb8828625e360362f80 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -1024,38 +1024,6 @@ void HeapObject::HeapObjectShortPrint(StringStream* accumulator) {
 }
 
 
-int HeapObject::SlowSizeFromMap(Map* map) {
-  // Avoid calling functions such as FixedArray::cast during GC, which
-  // read map pointer of this object again.
-  InstanceType instance_type = map->instance_type();
-  uint32_t type = static_cast<uint32_t>(instance_type);
-
-  if (instance_type < FIRST_NONSTRING_TYPE
-      && (StringShape(instance_type).IsSequential())) {
-    if ((type & kStringEncodingMask) == kAsciiStringTag) {
-      SeqAsciiString* seq_ascii_this = reinterpret_cast<SeqAsciiString*>(this);
-      return seq_ascii_this->SeqAsciiStringSize(instance_type);
-    } else {
-      SeqTwoByteString* self = reinterpret_cast<SeqTwoByteString*>(this);
-      return self->SeqTwoByteStringSize(instance_type);
-    }
-  }
-
-  switch (instance_type) {
-    case FIXED_ARRAY_TYPE:
-      return FixedArray::BodyDescriptor::SizeOf(map, this);
-    case BYTE_ARRAY_TYPE:
-      return reinterpret_cast<ByteArray*>(this)->ByteArraySize();
-    case CODE_TYPE:
-      return reinterpret_cast<Code*>(this)->CodeSize();
-    case MAP_TYPE:
-      return Map::kSize;
-    default:
-      return map->instance_size();
-  }
-}
-
-
 void HeapObject::Iterate(ObjectVisitor* v) {
   // Handle header
   IteratePointer(v, kMapOffset);