Replace Linked{Identity,Custom}Hash{Map,Set} with compact implementation; remove old code and flag.

runtime/vm/bootstrap_natives.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_BOOTSTRAP_NATIVES_H_
 #define VM_BOOTSTRAP_NATIVES_H_
 
 #include "vm/native_entry.h"
 
 // bootstrap dart natives used in the core dart library.
@@ skipping 342 matching lines @@
   V(LinkedHashMap_allocate, 1)                                                 \
   V(LinkedHashMap_getLength, 1)                                                \
   V(LinkedHashMap_insertOrUpdate, 3)                                           \
   V(LinkedHashMap_lookUp, 2)                                                   \
   V(LinkedHashMap_containsKey, 2)                                              \
   V(LinkedHashMap_remove, 2)                                                   \
   V(LinkedHashMap_clear, 1)                                                    \
   V(LinkedHashMap_toArray, 1)                                                  \
   V(LinkedHashMap_getModMark, 2)                                               \
   V(LinkedHashMap_useInternal, 0)                                              \
-  V(LinkedHashMap_useCompact, 0)                                               \
   V(WeakProperty_new, 2)                                                       \
   V(WeakProperty_getKey, 1)                                                    \
   V(WeakProperty_getValue, 1)                                                  \
   V(WeakProperty_setValue, 2)                                                  \
   V(Uri_isWindowsPlatform, 0)                                                  \
   V(LibraryPrefix_load, 1)                                                     \
   V(LibraryPrefix_invalidateDependentCode, 1)                                  \
   V(LibraryPrefix_loadError, 1)                                                \
   V(UserTag_new, 2)                                                            \
   V(UserTag_label, 1)                                                          \
@@ skipping 16 matching lines @@
   static void DN_##name(Dart_NativeArguments args);
 
   BOOTSTRAP_NATIVE_LIST(DECLARE_BOOTSTRAP_NATIVE)
 
 #undef DECLARE_BOOTSTRAP_NATIVE
 };
 
 }  // namespace dart
 
 #endif  // VM_BOOTSTRAP_NATIVES_H_