Reduce the number of captured variables in async code, by only capturing local

runtime/vm/symbols.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 VM_SYMBOLS_H_
 #define VM_SYMBOLS_H_
 
 #include "vm/growable_array.h"
 #include "vm/object.h"
 #include "vm/snapshot_ids.h"
@@ skipping 97 matching lines @@
   V(AsyncCatchErrorCallback, ":async_op_catch_error")                          \
   V(AsyncOperationParam, ":async_result")                                      \
   V(AsyncOperationErrorParam, ":async_error_param")                            \
   V(AsyncOperationStackTraceParam, ":async_stack_trace_param")                 \
   V(AsyncSavedTryCtxVarPrefix, ":async_saved_try_ctx_var_")                    \
   V(AsyncCatchHelper, "_asyncCatchHelper")                                     \
   V(AsyncThenWrapperHelper, "_asyncThenWrapperHelper")                         \
   V(AsyncErrorWrapperHelper, "_asyncErrorWrapperHelper")                       \
   V(AsyncAwaitHelper, "_awaitHelper")                                          \
   V(Await, "await")                                                            \
+  V(AwaitTempVarPrefix, ":await_temp_var_")                                    \
   V(AwaitContextVar, ":await_ctx_var")                                         \
   V(AwaitJumpVar, ":await_jump_var")                                           \
   V(Future, "Future")                                                          \
   V(FutureMicrotask, "Future.microtask")                                       \
   V(FutureValue, "Future.value")                                               \
   V(FutureThen, "then")                                                        \
   V(FutureCatchError, "catchError")                                            \
   V(Completer, "Completer")                                                    \
   V(CompleterComplete, "complete")                                             \
   V(CompleterCompleteError, "completeError")                                   \
@@ skipping 515 matching lines @@
   friend class SnapshotReader;
   friend class SnapshotWriter;
   friend class ApiMessageReader;
 
   DISALLOW_COPY_AND_ASSIGN(Symbols);
 };
 
 }  // namespace dart
 
 #endif  // VM_SYMBOLS_H_