Remove unused function form hydrogen instructions.

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
===================================================================
--- src/hydrogen-instructions.h	(revision 8219)
+++ src/hydrogen-instructions.h	(working copy)
@@ -727,10 +727,6 @@
   virtual void Verify();
 #endif
 
-  // Returns whether this is some kind of deoptimizing check
-  // instruction.
-  virtual bool IsCheckInstruction() const { return false; }
-
   virtual bool IsCall() { return false; }
 
   DECLARE_ABSTRACT_INSTRUCTION(Instruction)
@@ -1856,8 +1852,6 @@
     SetFlag(kDependsOnMaps);
   }
 
-  virtual bool IsCheckInstruction() const { return true; }
-
   virtual Representation RequiredInputRepresentation(int index) const {
     return Representation::Tagged();
   }
@@ -1891,8 +1885,6 @@
     SetFlag(kUseGVN);
   }
 
-  virtual bool IsCheckInstruction() const { return true; }
-
   virtual Representation RequiredInputRepresentation(int index) const {
     return Representation::Tagged();
   }
@@ -1933,8 +1925,6 @@
     return new HCheckInstanceType(value, IS_SYMBOL);
   }
 
-  virtual bool IsCheckInstruction() const { return true; }
-
   virtual Representation RequiredInputRepresentation(int index) const {
     return Representation::Tagged();
   }
@@ -1993,8 +1983,6 @@
     SetFlag(kUseGVN);
   }
 
-  virtual bool IsCheckInstruction() const { return true; }
-
   virtual Representation RequiredInputRepresentation(int index) const {
     return Representation::Tagged();
   }
@@ -2032,8 +2020,6 @@
     SetFlag(kDependsOnMaps);
   }
 
-  virtual bool IsCheckInstruction() const { return true; }
-
 #ifdef DEBUG
   virtual void Verify();
 #endif
@@ -2074,8 +2060,6 @@
     SetFlag(kUseGVN);
   }
 
-  virtual bool IsCheckInstruction() const { return true; }
-
   virtual Representation RequiredInputRepresentation(int index) const {
     return Representation::Tagged();
   }
@@ -2422,8 +2406,6 @@
     SetFlag(kUseGVN);
   }
 
-  virtual bool IsCheckInstruction() const { return true; }
-
   virtual Representation RequiredInputRepresentation(int index) const {
     return Representation::Integer32();
   }