Optimize clearing of map transitions.

src/heap/gc-tracer.h

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_HEAP_GC_TRACER_H_
 #define V8_HEAP_GC_TRACER_H_
 
 #include "src/base/platform/platform.h"
 #include "src/globals.h"
 
@@ skipping 112 matching lines @@
       MC_UPDATE_NEW_TO_NEW_POINTERS,
       MC_UPDATE_ROOT_TO_NEW_POINTERS,
       MC_UPDATE_OLD_TO_NEW_POINTERS,
       MC_UPDATE_POINTERS_TO_EVACUATED,
       MC_UPDATE_POINTERS_BETWEEN_EVACUATED,
       MC_UPDATE_MISC_POINTERS,
       MC_INCREMENTAL_FINALIZE,
       MC_WEAKCOLLECTION_PROCESS,
       MC_WEAKCOLLECTION_CLEAR,
       MC_WEAKCOLLECTION_ABORT,
-      MC_WEAKCELL,
-      MC_EXTRACT_DEPENDENT_CODE,
-      MC_NONLIVEREFERENCES,
-      MC_DEOPT_DEPENDENT_CODE,
+      MC_CLEAR,
+      MC_CLEAR_WEAKCELL,
+      MC_CLEAR_MAP,
+      MC_CLEAR_DEPENDENT_CODE,
       MC_FLUSH_CODE,
       SCAVENGER_CODE_FLUSH_CANDIDATES,
       SCAVENGER_OBJECT_GROUPS,
       SCAVENGER_OLD_TO_NEW_POINTERS,
       SCAVENGER_ROOTS,
       SCAVENGER_SCAVENGE,
       SCAVENGER_SEMISPACE,
       SCAVENGER_WEAK,
       NUMBER_OF_SCOPES
     };
@@ skipping 455 matching lines @@
 
   // Counts how many tracers were started without stopping.
   int start_counter_;
 
   DISALLOW_COPY_AND_ASSIGN(GCTracer);
 };
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_GC_TRACER_H_