Enable more redundancy elimination for checked mode asserts.

runtime/vm/intermediate_language.h

Index: runtime/vm/intermediate_language.h
===================================================================
--- runtime/vm/intermediate_language.h	(revision 13738)
+++ runtime/vm/intermediate_language.h	(working copy)
@@ -1910,8 +1910,13 @@
 
   virtual bool HasSideEffect() const { return false; }
 
+  virtual bool AffectedBySideEffect() const { return false; }
+  virtual bool AttributesEqual(Instruction* other) const;
+
   virtual intptr_t ResultCid() const { return kDynamicCid; }
 
+  virtual Definition* Canonicalize();
+
  private:
   const intptr_t token_pos_;
   const AbstractType& dst_type_;
@@ -1951,6 +1956,9 @@
 
   virtual bool HasSideEffect() const { return false; }
 
+  virtual bool AffectedBySideEffect() const { return false; }
+  virtual bool AttributesEqual(Instruction* other) const { return true; }
+
   virtual intptr_t ResultCid() const { return kBoolCid; }
 
   virtual Definition* Canonicalize();