[turbofan] Remove unused function_type_ from Typer.

src/compiler/typer.h

Index: src/compiler/typer.h
diff --git a/src/compiler/typer.h b/src/compiler/typer.h
index b6c5cb333cae56d50776baeadc6e8c1368e574c2..056318755e660dc18c8b7591b1847007d38dcdf1 100644
--- a/src/compiler/typer.h
+++ b/src/compiler/typer.h
@@ -31,8 +31,7 @@ class Typer {
   typedef base::Flags<Flag> Flags;
 
   Typer(Isolate* isolate, Graph* graph, Flags flags = kNoFlags,
-        CompilationDependencies* dependencies = nullptr,
-        FunctionType* function_type = nullptr);
+        CompilationDependencies* dependencies = nullptr);
   ~Typer();
 
   void Run();
@@ -48,14 +47,12 @@ class Typer {
   Isolate* isolate() const { return isolate_; }
   Flags flags() const { return flags_; }
   CompilationDependencies* dependencies() const { return dependencies_; }
-  FunctionType* function_type() const { return function_type_; }
   OperationTyper* operation_typer() { return &operation_typer_; }
 
   Isolate* const isolate_;
   Graph* const graph_;
   Flags const flags_;
   CompilationDependencies* const dependencies_;
-  FunctionType* function_type_;
   Decorator* decorator_;
   TypeCache const& cache_;
   OperationTyper operation_typer_;