[WIP] Initial CallFunctionCallback 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 e60fbe33fe57c355131d7a1cd6311dbf69af671c..a3f64a54afd6fafff7183bbb4e8c9b1165400fba 100644
--- a/src/arm64/macro-assembler-arm64.h
+++ b/src/arm64/macro-assembler-arm64.h
@@ -1009,6 +1009,9 @@ class MacroAssembler : public Assembler {
   // via --debug-code.
   void AssertUndefinedOrAllocationSite(Register object, Register scratch);
 
+  // Abort if argument is not a valid API call result, enabled via --debug-code.
+  void AssertApiCallResult(Register object);
+
   // Abort execution if argument is not a positive or zero integer, enabled via
   // --debug-code.
   void AssertPositiveOrZero(Register value);