Simplify stack check instruction in Crankshaft.

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
===================================================================
--- src/hydrogen-instructions.h	(revision 10109)
+++ src/hydrogen-instructions.h	(working copy)
@@ -1271,12 +1271,7 @@
 
 class HStackCheck: public HTemplateInstruction<1> {
  public:
-  enum Type {
-    kFunctionEntry,
-    kBackwardsBranch
-  };
-
-  HStackCheck(HValue* context, Type type) : type_(type) {
+  explicit HStackCheck(HValue* context) {
     SetOperandAt(0, context);
   }
 
@@ -1294,13 +1289,7 @@
     }
   }
 
-  bool is_function_entry() { return type_ == kFunctionEntry; }
-  bool is_backwards_branch() { return type_ == kBackwardsBranch; }
-
   DECLARE_CONCRETE_INSTRUCTION(StackCheck)
-
- private:
-  Type type_;
 };