Remove guard page mechanism from promotion queue.

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 "src/allocation.h"
@@ skipping 365 matching lines @@
         heap_(heap) {}
 
   void Initialize();
 
   void Destroy() {
     DCHECK(is_empty());
     delete emergency_stack_;
     emergency_stack_ = NULL;
   }
 
-  inline void ActivateGuardIfOnTheSamePage();
-
   Page* GetHeadPage() {
     return Page::FromAllocationTop(reinterpret_cast<Address>(rear_));
   }
 
   void SetNewLimit(Address limit) {
-    if (!guard_) {
-      return;
-    }
-
-    DCHECK(GetHeadPage() == Page::FromAllocationTop(limit));
     limit_ = reinterpret_cast<intptr_t*>(limit);
 
     if (limit_ <= rear_) {
       return;
     }
 
     RelocateQueueHead();
   }
 
   bool IsBelowPromotionQueue(Address to_space_top) {
@@ skipping 36 matching lines @@
     SemiSpace::AssertValidRange(reinterpret_cast<Address>(rear_),
                                 reinterpret_cast<Address>(front_));
   }
 
  private:
   // The front of the queue is higher in the memory page chain than the rear.
   intptr_t* front_;
   intptr_t* rear_;
   intptr_t* limit_;
 
-  bool guard_;
-
   static const int kEntrySizeInWords = 2;
 
   struct Entry {
     Entry(HeapObject* obj, int size) : obj_(obj), size_(size) {}
 
     HeapObject* obj_;
     int size_;
   };
   List<Entry>* emergency_stack_;
 
@@ skipping 2033 matching lines @@
   DisallowHeapAllocation no_allocation;  // i.e. no gc allowed.
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
 };
 #endif  // DEBUG
 }
 }  // namespace v8::internal
 
 #endif  // V8_HEAP_HEAP_H_