Remove guard page mechanism from promotion queue.

src/heap/heap.h

Index: src/heap/heap.h
diff --git a/src/heap/heap.h b/src/heap/heap.h
index 8b4a021e7595eb3e5cde01aa1ae774ca2ed37ba5..8a449cb4ae853a4fbebea1d4211bb4330ab1d332 100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -383,18 +383,11 @@ class PromotionQueue {
     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_) {
@@ -451,8 +444,6 @@ class PromotionQueue {
   intptr_t* rear_;
   intptr_t* limit_;
 
-  bool guard_;
-
   static const int kEntrySizeInWords = 2;
 
   struct Entry {