Oilpan: We shouldn't calculate allocationSizeFromSize twice

Source/platform/heap/Heap.h

Index: Source/platform/heap/Heap.h
diff --git a/Source/platform/heap/Heap.h b/Source/platform/heap/Heap.h
index 6c4781dec79f3c8180ed80eb1a2ec8bec88f4669..50955889aa27a258b004efcf5e75e30412815cac 100644
--- a/Source/platform/heap/Heap.h
+++ b/Source/platform/heap/Heap.h
@@ -816,7 +816,7 @@ public:
 
 private:
     void addPageToHeap(const GCInfo*);
-    PLATFORM_EXPORT Address outOfLineAllocate(size_t, const GCInfo*);
+    PLATFORM_EXPORT Address outOfLineAllocate(size_t payloadSize, size_t allocationSize, const GCInfo*);
     static size_t allocationSizeFromSize(size_t);
     PLATFORM_EXPORT Address allocateLargeObject(size_t, const GCInfo*);
     Address currentAllocationPoint() const { return m_currentAllocationPoint; }
@@ -1402,7 +1402,7 @@ Address ThreadHeap<Header>::allocate(size_t size, const GCInfo* gcInfo)
         ASSERT(heapPageFromAddress(headerAddress + allocationSize - 1));
         return result;
     }
-    return outOfLineAllocate(size, gcInfo);
+    return outOfLineAllocate(size, allocationSize, gcInfo);
 }
 
 template<typename T, typename HeapTraits>