Implement in-heap backing store for typed arrays.

src/factory.h

Index: src/factory.h
diff --git a/src/factory.h b/src/factory.h
index 92086d4b304d1e477937e4712ce7bc69d40ca24d..d67796e2b21b27175f7a28990ca5ee3215310650 100644
--- a/src/factory.h
+++ b/src/factory.h
@@ -252,6 +252,11 @@ class Factory {
       void* external_pointer,
       PretenureFlag pretenure = NOT_TENURED);
 
+  Handle<FixedTypedArrayBase> NewFixedTypedArray(
+      int length,
+      ExternalArrayType array_type,
+      PretenureFlag pretenure = NOT_TENURED);
+
   Handle<Cell> NewCell(Handle<Object> value);
 
   Handle<PropertyCell> NewPropertyCellWithHole();