Add SIMD 128 alignment support to Heap.

src/heap/spaces-inl.h

Index: src/heap/spaces-inl.h
diff --git a/src/heap/spaces-inl.h b/src/heap/spaces-inl.h
index 0cbabbaf683f9327c8fc4b6eae2ddf0adb65b190..c2c4d126976336dd4348d0e76c4575b3f9748218 100644
--- a/src/heap/spaces-inl.h
+++ b/src/heap/spaces-inl.h
@@ -311,6 +311,9 @@ AllocationResult PagedSpace::AllocateRawAligned(int size_in_bytes,
     if (object != NULL && filler_size != 0) {
       object = heap()->AlignWithFiller(object, size_in_bytes, allocation_size,
                                        alignment);
+      // Filler objects are initialized, so mark only the aligned object memory
+      // as uninitialized.
+      allocation_size = size_in_bytes;
     }
   }