Introduce safe interface to "copy and grow" FixedArray.

src/factory.cc

Index: src/factory.cc
diff --git a/src/factory.cc b/src/factory.cc
index ea4f69a96b863957f6de9255e4f649e4096875f1..bc5d1e4e0ecbd424df06bcf248678116d5fcbfda 100644
--- a/src/factory.cc
+++ b/src/factory.cc
@@ -978,6 +978,14 @@ Handle<FixedArray> Factory::CopyFixedArrayWithMap(Handle<FixedArray> array,
 }
 
 
+Handle<FixedArray> Factory::CopyFixedArrayAndGrow(Handle<FixedArray> array,
+                                                  int grow_by) {
+  CALL_HEAP_FUNCTION(isolate(),
+                     isolate()->heap()->CopyFixedArrayAndGrow(*array, grow_by),
+                     FixedArray);
+}
+
+
 Handle<FixedArray> Factory::CopyFixedArray(Handle<FixedArray> array) {
   CALL_HEAP_FUNCTION(isolate(),
                      isolate()->heap()->CopyFixedArray(*array),