[turbofan] Implement the call protocol properly for direct calls.

src/arm/macro-assembler-arm.h

Index: src/arm/macro-assembler-arm.h
diff --git a/src/arm/macro-assembler-arm.h b/src/arm/macro-assembler-arm.h
index 6f176e6afccbdc8884d9a4500eceb24e7bf24671..8ab676f39b2a91d13c6567da46fc7370810b952c 100644
--- a/src/arm/macro-assembler-arm.h
+++ b/src/arm/macro-assembler-arm.h
@@ -23,6 +23,7 @@ const Register kInterpreterRegisterFileRegister = {Register::kCode_r4};
 const Register kInterpreterBytecodeOffsetRegister = {Register::kCode_r5};
 const Register kInterpreterBytecodeArrayRegister = {Register::kCode_r6};
 const Register kInterpreterDispatchTableRegister = {Register::kCode_r8};
+const Register kJavaScriptCallArgCountRegister = {Register::kCode_r0};
 const Register kRuntimeCallFunctionRegister = {Register::kCode_r1};
 const Register kRuntimeCallArgCountRegister = {Register::kCode_r0};