Adds the possibility of setting a Code object as the callback of a FunctionTemplate.

src/ic/arm64/handler-compiler-arm64.cc

Index: src/ic/arm64/handler-compiler-arm64.cc
diff --git a/src/ic/arm64/handler-compiler-arm64.cc b/src/ic/arm64/handler-compiler-arm64.cc
index e5f872dd9778188bb490b6f721e63bdad519ceca..1dd52f86e560589f921489310cd03b63d2b88d98 100644
--- a/src/ic/arm64/handler-compiler-arm64.cc
+++ b/src/ic/arm64/handler-compiler-arm64.cc
@@ -207,6 +207,13 @@ void PropertyHandlerCompiler::GenerateApiAccessorCall(
     __ Ldr(data, FieldMemOperand(data, CallHandlerInfo::kDataOffset));
   }
 
+  if (api_call_info->fast_handler()->IsCode()) {
+    // Just tail call into the fast handler if present.
+    __ Jump(handle(Code::cast(api_call_info->fast_handler())),
+            RelocInfo::CODE_TARGET);
+    return;
+  }
+
   // Put api_function_address in place.
   Address function_address = v8::ToCData<Address>(api_call_info->callback());
   ApiFunction fun(function_address);