Add a new API function to extract all the native arguments into an array

runtime/vm/raw_object.h

Index: runtime/vm/raw_object.h
===================================================================
--- runtime/vm/raw_object.h	(revision 36461)
+++ runtime/vm/raw_object.h	(working copy)
@@ -259,7 +259,7 @@
       return SizeBits::update(SizeToTagValue(size), tag);
     }
 
-  private:
+   private:
     // The actual unscaled bit field used within the tag field.
     class SizeBits : public BitField<intptr_t, kSizeTagPos, kSizeTagSize> {};
 
@@ -1259,6 +1259,7 @@
 
   int64_t value_;
 
+  friend class Api;
   friend class SnapshotReader;
 };
 
@@ -1289,6 +1290,7 @@
 
   double value_;
 
+  friend class Api;
   friend class SnapshotReader;
 };