Implement core support for FixedDoubleArrays.

src/factory.h

Index: src/factory.h
diff --git a/src/factory.h b/src/factory.h
index 55d1e9a174550ced4914035086a9eeec33540feb..81c543cbe6ba3a2c94b7328efb62410e78cb5800 100644
--- a/src/factory.h
+++ b/src/factory.h
@@ -49,6 +49,11 @@ class Factory {
       int size,
       PretenureFlag pretenure = NOT_TENURED);
 
+  // Allocate a new fixed array with undefined entries.
+  Handle<FixedArray> NewFixedDoubleArray(
+      int size,
+      PretenureFlag pretenure = NOT_TENURED);
+
   Handle<NumberDictionary> NewNumberDictionary(int at_least_space_for);
 
   Handle<StringDictionary> NewStringDictionary(int at_least_space_for);