Simplify IdentityMap.

src/heap/heap.h

 // Copyright 2012 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_HEAP_H_
 #define V8_HEAP_HEAP_H_
 
 #include <cmath>
 #include <map>
 
@@ skipping 602 matching lines @@
     explicit RelocationLock(Heap* heap) : heap_(heap) {
       heap_->relocation_mutex_.Lock();
     }
 
     ~RelocationLock() { heap_->relocation_mutex_.Unlock(); }
 
    private:
     Heap* heap_;
   };
 
-  // An optional version of the above lock that can be used for some critical
-  // sections on the mutator thread; only safe since the GC currently does not
-  // do concurrent compaction.
-  class OptionalRelocationLock {
-   public:
-    OptionalRelocationLock(Heap* heap, bool concurrent)
-        : heap_(heap), concurrent_(concurrent) {
-      if (concurrent_) heap_->relocation_mutex_.Lock();
-    }
-
-    ~OptionalRelocationLock() {
-      if (concurrent_) heap_->relocation_mutex_.Unlock();
-    }
-
-   private:
-    Heap* heap_;
-    bool concurrent_;
-  };
-
   // Support for partial snapshots.  After calling this we have a linear
   // space to write objects in each space.
   struct Chunk {
     uint32_t size;
     Address start;
     Address end;
   };
   typedef List<Chunk> Reservation;
 
   static const intptr_t kMinimumOldGenerationAllocationLimit =
@@ skipping 2083 matching lines @@
   DisallowHeapAllocation no_allocation;  // i.e. no gc allowed.
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
 };
 #endif  // DEBUG
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_HEAP_H_