Make subtype test cache stub shared between isolates.

runtime/vm/assembler_arm64.h

 // Copyright (c) 2014, 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 VM_ASSEMBLER_ARM64_H_
 #define VM_ASSEMBLER_ARM64_H_
 
 #ifndef VM_ASSEMBLER_H_
 #error Do not include assembler_arm64.h directly; use assembler.h instead.
 #endif
@@ skipping 1301 matching lines @@
   void LoadWordFromPoolOffsetFixed(Register dst, Register pp, uint32_t offset);
   intptr_t FindImmediate(int64_t imm);
   bool CanLoadFromObjectPool(const Object& object) const;
   bool CanLoadImmediateFromPool(int64_t imm, Register pp);
   void LoadExternalLabel(Register dst, const ExternalLabel* label,
                          Patchability patchable, Register pp);
   void LoadExternalLabelFixed(Register dst,
                               const ExternalLabel* label,
                               Patchability patchable,
                               Register pp);
-  void LoadIsolate(Register dst, Register pp);
+  void LoadIsolate(Register dst);
   void LoadObject(Register dst, const Object& obj, Register pp);
   void LoadUniqueObject(Register dst, const Object& obj, Register pp);
   void LoadDecodableImmediate(Register reg, int64_t imm, Register pp);
   void LoadImmediateFixed(Register reg, int64_t imm);
   void LoadImmediate(Register reg, int64_t imm, Register pp);
   void LoadDImmediate(VRegister reg, double immd, Register pp);
 
   void PushObject(const Object& object, Register pp) {
     LoadObject(TMP, object, pp);
     Push(TMP);
@@ skipping 616 matching lines @@
                                   Register value,
                                   Label* no_update);
 
   DISALLOW_ALLOCATION();
   DISALLOW_COPY_AND_ASSIGN(Assembler);
 };
 
 }  // namespace dart
 
 #endif  // VM_ASSEMBLER_ARM64_H_