Remove duplicated initialization of stack_parameter_count_ of hydrogen stub descriptor.

src/x64/code-stubs-x64.cc

Index: src/x64/code-stubs-x64.cc
===================================================================
--- src/x64/code-stubs-x64.cc	(revision 14866)
+++ src/x64/code-stubs-x64.cc	(working copy)
@@ -46,7 +46,6 @@
   static Register registers[] = { rax, rbx, rcx };
   descriptor->register_param_count_ = 3;
   descriptor->register_params_ = registers;
-  descriptor->stack_parameter_count_ = NULL;
   descriptor->deoptimization_handler_ =
       Runtime::FunctionForId(Runtime::kCreateArrayLiteralShallow)->entry;
 }
@@ -58,7 +57,6 @@
   static Register registers[] = { rax, rbx, rcx, rdx };
   descriptor->register_param_count_ = 4;
   descriptor->register_params_ = registers;
-  descriptor->stack_parameter_count_ = NULL;
   descriptor->deoptimization_handler_ =
       Runtime::FunctionForId(Runtime::kCreateObjectLiteralShallow)->entry;
 }
@@ -81,7 +79,6 @@
   static Register registers[] = { rax };
   descriptor->register_param_count_ = 1;
   descriptor->register_params_ = registers;
-  descriptor->stack_parameter_count_ = NULL;
   descriptor->deoptimization_handler_ = NULL;
 }
 
@@ -92,7 +89,6 @@
   static Register registers[] = { rdx };
   descriptor->register_param_count_ = 1;
   descriptor->register_params_ = registers;
-  descriptor->stack_parameter_count_ = NULL;
   descriptor->deoptimization_handler_ = NULL;
 }