Make ImmutableArray a sub class of AllStatic.

runtime/vm/object.cc

Index: runtime/vm/object.cc
===================================================================
--- runtime/vm/object.cc	(revision 23868)
+++ runtime/vm/object.cc	(working copy)
@@ -530,7 +530,7 @@
   cls = Class::New<Array>();
   isolate->object_store()->set_array_class(cls);
   cls.set_type_arguments_field_offset(Array::type_arguments_offset());
-  cls = Class::New<ImmutableArray>();
+  cls = Class::New<Array>(kImmutableArrayCid);
   isolate->object_store()->set_immutable_array_class(cls);
   cls.set_type_arguments_field_offset(Array::type_arguments_offset());
   cls = Class::NewStringClass(kOneByteStringCid);
@@ -832,10 +832,11 @@
   RegisterPrivateClass(cls, Symbols::GrowableObjectArray(), core_lib);
   pending_classes.Add(cls, Heap::kOld);
 
-  cls = Class::New<ImmutableArray>();
+  cls = Class::New<Array>(kImmutableArrayCid);
   object_store->set_immutable_array_class(cls);
   cls.set_type_arguments_field_offset(Array::type_arguments_offset());
   ASSERT(object_store->immutable_array_class() != object_store->array_class());
+  cls.set_is_prefinalized();
   RegisterPrivateClass(cls, Symbols::ImmutableArray(), core_lib);
   pending_classes.Add(cls, Heap::kOld);
 
@@ -1120,7 +1121,7 @@
   cls = Class::New<Array>();
   object_store->set_array_class(cls);
 
-  cls = Class::New<ImmutableArray>();
+  cls = Class::New<Array>(kImmutableArrayCid);
   object_store->set_immutable_array_class(cls);
 
   cls = Class::New<GrowableObjectArray>();
@@ -12542,9 +12543,10 @@
 
 const char* Array::ToCString() const {
   if (IsNull()) {
-    return "Array NULL";
+    return IsImmutable() ? "ImmutableArray NULL" : "Array NULL";
   }
-  const char* format = "Array len:%"Pd"";
+  const char* format = !IsImmutable() ? "Array len:%"Pd"" :
+      "Immutable Array len:%"Pd"";
   intptr_t len = OS::SNPrint(NULL, 0, format, Length()) + 1;
   char* chars = Isolate::Current()->current_zone()->Alloc<char>(len);
   OS::SNPrint(chars, len, format, Length());
@@ -12612,18 +12614,6 @@
 }
 
 
-const char* ImmutableArray::ToCString() const {
-  if (IsNull()) {
-    return "ImmutableArray NULL";
-  }
-  const char* format = "ImmutableArray len:%"Pd"";
-  intptr_t len = OS::SNPrint(NULL, 0, format, Length()) + 1;
-  char* chars = Isolate::Current()->current_zone()->Alloc<char>(len);
-  OS::SNPrint(chars, len, format, Length());
-  return chars;
-}
-
-
 void GrowableObjectArray::Add(const Object& value, Heap::Space space) const {
   ASSERT(!IsNull());
   if (Length() == Capacity()) {