Fast-codegen: Arguments object working on all platforms.

src/x64/macro-assembler-x64.h

Index: src/x64/macro-assembler-x64.h
diff --git a/src/x64/macro-assembler-x64.h b/src/x64/macro-assembler-x64.h
index e0af1edc7a4b865507cf9cdec45d014f0db4b8b2..9e7c25c955f0ca923e26816718a6d119e93268ea 100644
--- a/src/x64/macro-assembler-x64.h
+++ b/src/x64/macro-assembler-x64.h
@@ -548,6 +548,9 @@ class MacroAssembler: public Assembler {
   // occurred.
   void IllegalOperation(int num_arguments);
 
+  // Find the function context up the context chain.
+  void LoadContext(Register dst, int context_chain_length);
+
   // ---------------------------------------------------------------------------
   // Runtime calls