Optimizes 'as' operation in similar way as 'instanceof': collect type feedback in unoptimized mode…

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/object.h"
 #include "vm/snapshot_ids.h"
 
@@ skipping 208 matching lines @@
   V(MegamorphicMiss, "megamorphic_miss")                                       \
   V(CommaSpace, ", ")                                                          \
   V(ColonSpace, ": ")                                                          \
   V(RParenArrow, ") => ")                                                      \
   V(SpaceExtendsSpace, " extends ")                                            \
   V(PatchSpace, "patch ")                                                      \
   V(SwitchExpr, ":switch_expr")                                                \
   V(TwoNewlines, "\n\n")                                                       \
   V(TwoSpaces, "  ")                                                           \
   V(_instanceOf, "_instanceOf")                                                \
+  V(_as, "_as")                                                                \
   V(PrivateGetterPrefix, "get:_")                                              \
   V(PrivateSetterPrefix, "set:_")                                              \
   V(_New, "_new")                                                              \
   V(DartScheme, "dart:")                                                       \
   V(DartSchemePrivate, "dart:_")                                               \
   V(DartCore, "dart:core")                                                     \
   V(DartCollection, "dart:collection")                                         \
   V(DartCollectionDev, "dart:_collection-dev")                                 \
   V(DartMath, "dart:math")                                                     \
   V(DartIsolate, "dart:isolate")                                               \
@@ skipping 197 matching lines @@
   friend class SnapshotReader;
   friend class SnapshotWriter;
   friend class ApiMessageReader;
 
   DISALLOW_COPY_AND_ASSIGN(Symbols);
 };
 
 }  // namespace dart
 
 #endif  // VM_SYMBOLS_H_