Add an external array type to support typed arrays.

runtime/vm/object_store.h

Index: runtime/vm/object_store.h
diff --git a/runtime/vm/object_store.h b/runtime/vm/object_store.h
index 2149772d9b3c303e99bd13719281f9772201d505..8882a2b5942653446386f95a31b00ea87f939162 100644
--- a/runtime/vm/object_store.h
+++ b/runtime/vm/object_store.h
@@ -46,6 +46,7 @@ class ObjectStore {
     kBoolClass,
     kArrayClass,
     kImmutableArrayClass,
+    kByteBufferClass,
     kUnhandledExceptionClass,
     kStacktraceClass,
     kJSRegExpClass,
@@ -148,6 +149,11 @@ class ObjectStore {
     immutable_array_class_ = value.raw();
   }
 
+  RawClass* byte_buffer_class() const { return byte_buffer_class_; }
+  void set_byte_buffer_class(const Class& value) {
+    byte_buffer_class_ = value.raw();
+  }
+
   RawClass* unhandled_exception_class() const {
     return unhandled_exception_class_;
   }
@@ -264,6 +270,7 @@ class ObjectStore {
   RawType* list_interface_;
   RawClass* array_class_;
   RawClass* immutable_array_class_;
+  RawClass* byte_buffer_class_;
   RawClass* unhandled_exception_class_;
   RawClass* stacktrace_class_;
   RawClass* jsregexp_class_;