Fix has_constant_parameter_count() confusion in LReturn

src/arm/lithium-codegen-arm.cc

Index: src/arm/lithium-codegen-arm.cc
diff --git a/src/arm/lithium-codegen-arm.cc b/src/arm/lithium-codegen-arm.cc
index e945a13c8788df96de7bf578fab5957ccd6f1d75..e323e0d210b3e8bc3280555cb612db07ea5b143d 100644
--- a/src/arm/lithium-codegen-arm.cc
+++ b/src/arm/lithium-codegen-arm.cc
@@ -2964,6 +2964,7 @@ void LCodeGen::DoReturn(LReturn* instr) {
         __ add(sp, sp, Operand(sp_delta));
       }
     } else {
+      DCHECK(info()->IsStub());  // Functions would need to drop one more value.
       Register reg = ToRegister(instr->parameter_count());
       // The argument count parameter is a smi
       __ SmiUntag(reg);