Track async causal stack traces

runtime/vm/stub_code_arm64.cc

 // 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.
 
 #include "vm/globals.h"
 #if defined(TARGET_ARCH_ARM64)
 
 #include "vm/assembler.h"
 #include "vm/code_generator.h"
 #include "vm/compiler.h"
@@ skipping 2315 matching lines @@
   __ ldr(CODE_REG, Address(THR, Thread::ic_lookup_through_code_stub_offset()));
   __ ldr(R1, FieldAddress(CODE_REG, Code::checked_entry_point_offset()));
   __ br(R1);
 }
 
 
 void StubCode::GenerateFrameAwaitingMaterializationStub(Assembler* assembler) {
   __ brk(0);
 }
 
+
+void StubCode::GenerateAsynchronousGapMarkerStub(Assembler* assembler) {
+  __ brk(0);
+}
+
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM64