Make CTX allocatable by the register allocator.

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 40 matching lines @@
   V(ListFactory, "List.")                                                      \
   V(Map, "Map")                                                                \
   V(MapLiteralFactory, "Map._fromLiteral")                                     \
   V(ImmutableMap, "ImmutableMap")                                              \
   V(ImmutableMapConstructor, "ImmutableMap._create")                           \
   V(StringBase, "_StringBase")                                                 \
   V(Interpolate, "_interpolate")                                               \
   V(InterpolateSingle, "_interpolateSingle")                                   \
   V(GetIterator, "iterator")                                                   \
   V(NoSuchMethod, "noSuchMethod")                                              \
-  V(SavedCurrentContextVar, ":saved_current_context_var")                      \
+  V(CurrentContextVar, ":current_context_var")                                 \
   V(SavedEntryContextVar, ":saved_entry_context_var")                          \
   V(SavedTryContextVar, ":saved_try_context_var")                              \
   V(ExceptionParameter, ":exception")                                          \
   V(StackTraceParameter, ":stack_trace")                                       \
   V(ExceptionVar, ":exception_var")                                            \
   V(StackTraceVar, ":stack_trace_var")                                         \
   V(ListLiteralElement, "list literal element")                                \
   V(ForInIter, ":for-in-iter")                                                 \
   V(Library, "library")                                                        \
   V(LoadLibrary, "loadLibrary")                                                \
@@ skipping 445 matching lines @@
   friend class SnapshotReader;
   friend class SnapshotWriter;
   friend class ApiMessageReader;
 
   DISALLOW_COPY_AND_ASSIGN(Symbols);
 };
 
 }  // namespace dart
 
 #endif  // VM_SYMBOLS_H_