Move double alignment logic into memory allocator.

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 696 matching lines @@
   bool CanExpandOldGeneration(int size) {
     return (CommittedOldGenerationMemory() + size) < MaxOldGenerationSize();
   }
 
   // Returns a deep copy of the JavaScript object.
   // Properties and elements are copied too.
   // Optionally takes an AllocationSite to be appended in an AllocationMemento.
   MUST_USE_RESULT AllocationResult
       CopyJSObject(JSObject* source, AllocationSite* site = NULL);
 
+  // This method assumes overallocation of one word. It will store a filler
+  // before the object if the given object is not double aligned, otherwise
+  // it will place the filler after the object.
+  MUST_USE_RESULT HeapObject* EnsureDoubleAligned(HeapObject* object, int size);
+
   // Clear the Instanceof cache (used when a prototype changes).
   inline void ClearInstanceofCache();
 
   // Iterates the whole code space to clear all ICs of the given kind.
   void ClearAllICsByKind(Code::Kind kind);
 
   // FreeSpace objects have a null map after deserialization. Update the map.
   void RepairFreeListsAfterDeserialization();
 
   template <typename T>
@@ skipping 1881 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_