Make stack_parameter_count a plain register.

src/mips/deoptimizer-mips.cc

Index: src/mips/deoptimizer-mips.cc
diff --git a/src/mips/deoptimizer-mips.cc b/src/mips/deoptimizer-mips.cc
index 4426d90b7396b231db25bbbd95f2189ed29db3c0..d31990be5c7eb8a7aeef73f2e47bc9e6ff03828b 100644
--- a/src/mips/deoptimizer-mips.cc
+++ b/src/mips/deoptimizer-mips.cc
@@ -104,10 +104,7 @@ void Deoptimizer::SetPlatformCompiledStubRegisters(
   ApiFunction function(descriptor->deoptimization_handler_);
   ExternalReference xref(&function, ExternalReference::BUILTIN_CALL, isolate_);
   intptr_t handler = reinterpret_cast<intptr_t>(xref.address());
-  int params = descriptor->register_param_count_;
-  if (descriptor->stack_parameter_count_ != NULL) {
-    params++;
-  }
+  int params = descriptor->environment_length();
   output_frame->SetRegister(s0.code(), params);
   output_frame->SetRegister(s1.code(), (params - 1) * kPointerSize);
   output_frame->SetRegister(s2.code(), handler);