Create string efficiently from Uint16List/View.

runtime/vm/object.h

Index: runtime/vm/object.h
diff --git a/runtime/vm/object.h b/runtime/vm/object.h
index 9adf1345e35e29ebff8b712334f2b9a3015125ef..17b476e2e64008341cfe02cde389ac7f3a123dcf 100644
--- a/runtime/vm/object.h
+++ b/runtime/vm/object.h
@@ -6124,6 +6124,16 @@ class TwoByteString : public AllStatic {
   static RawTwoByteString* New(const String& str,
                                Heap::Space space);
 
+  static RawTwoByteString* New(const TypedData& other_typed_data,
+                               intptr_t other_start_index,
+                               intptr_t other_len,
+                               Heap::Space space = Heap::kNew);
+
+  static RawTwoByteString* New(const ExternalTypedData& other_typed_data,
+                               intptr_t other_start_index,
+                               intptr_t other_len,
+                               Heap::Space space = Heap::kNew);
+
   static RawTwoByteString* Concat(const String& str1,
                                   const String& str2,
                                   Heap::Space space);