[builtins] Start refactoring the Apply builtin.

src/arm64/macro-assembler-arm64.h

Index: src/arm64/macro-assembler-arm64.h
diff --git a/src/arm64/macro-assembler-arm64.h b/src/arm64/macro-assembler-arm64.h
index bc2d9b39ac056e2333d8c32631e1bdc70ab154f2..28a1d5bdc6aa0a730bbbabe1c8536439f7350278 100644
--- a/src/arm64/macro-assembler-arm64.h
+++ b/src/arm64/macro-assembler-arm64.h
@@ -1565,6 +1565,9 @@ class MacroAssembler : public Assembler {
   inline void ObjectTag(Register tagged_obj, Register obj);
   inline void ObjectUntag(Register untagged_obj, Register obj);
 
+  // Abort execution if argument is not a FixedArray, enabled via --debug-code.
+  void AssertFixedArray(Register object);
+
   // Abort execution if argument is not a JSFunction, enabled via --debug-code.
   void AssertFunction(Register object);