[vm] Remove Dart_MakeExternalString and --support-externalizable-strings

runtime/vm/object.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef RUNTIME_VM_OBJECT_H_
 #define RUNTIME_VM_OBJECT_H_
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "platform/utils.h"
@@ skipping 3357 matching lines @@
   bool is_unboxing_candidate() const {
     return UnboxingCandidateBit::decode(raw_ptr()->kind_bits_);
   }
   // Default 'true', set to false once optimizing compiler determines it should
   // be boxed.
   void set_is_unboxing_candidate(bool b) const {
     ASSERT(IsOriginal());
     set_kind_bits(UnboxingCandidateBit::update(b, raw_ptr()->kind_bits_));
   }
 
-  static bool IsExternalizableCid(intptr_t cid);
-
   enum {
     kUnknownLengthOffset = -1,
     kUnknownFixedLength = -1,
     kNoFixedLength = -2,
   };
   // Returns false if any value read from this field is guaranteed to be
   // not null.
   // Internally we is_nullable_ field contains either kNullCid (nullable) or
   // any other value (non-nullable) instead of boolean. This is done to simplify
   // guarding sequence in the generated code.
@@ skipping 3533 matching lines @@
   }
 
   bool IsExternal() const {
     return RawObject::IsExternalStringClassId(raw()->GetClassId());
   }
 
   void* GetPeer() const;
 
   void ToUTF8(uint8_t* utf8_array, intptr_t array_len) const;
 
-  // Copies the string characters into the provided external array
-  // and morphs the string object into an external string object.
-  // The remaining unused part of the original string object is marked as
-  // an Array object or a regular Object so that it can be traversed during
-  // garbage collection.
-  RawString* MakeExternal(void* array,
-                          intptr_t external_size,
-                          void* peer,
-                          Dart_PeerFinalizer cback) const;
-
   // Creates a new String object from a C string that is assumed to contain
   // UTF-8 encoded characters and '\0' is considered a termination character.
   // TODO(7123) - Rename this to FromCString(....).
   static RawString* New(const char* cstr, Heap::Space space = Heap::kNew);
 
   // Creates a new String object from an array of UTF-8 encoded characters.
   static RawString* FromUTF8(const uint8_t* utf8_array,
                              intptr_t array_len,
                              Heap::Space space = Heap::kNew);
 
@@ skipping 2053 matching lines @@
 
 inline void TypeArguments::SetHash(intptr_t value) const {
   // This is only safe because we create a new Smi, which does not cause
   // heap allocation.
   StoreSmi(&raw_ptr()->hash_, Smi::New(value));
 }
 
 }  // namespace dart
 
 #endif  // RUNTIME_VM_OBJECT_H_