Fix broken use lists in branch instructions.

runtime/vm/intermediate_language.h

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_INTERMEDIATE_LANGUAGE_H_
 #define VM_INTERMEDIATE_LANGUAGE_H_
 
 #include "vm/allocation.h"
 #include "vm/ast.h"
 #include "vm/growable_array.h"
@@ skipping 1658 matching lines @@
 
   virtual intptr_t ArgumentCount() const;
   intptr_t InputCount() const;
   Value* InputAt(intptr_t i) const;
   void SetInputAt(intptr_t i, Value* value);
   virtual bool CanDeoptimize() const;
 
   virtual bool HasSideEffect() const;
 
   ComparisonInstr* comparison() const { return comparison_; }
-  void set_comparison(ComparisonInstr* value) { comparison_ = value; }
+  void SetComparison(ComparisonInstr* comp);
 
   bool is_checked() const { return is_checked_; }
 
   virtual LocationSummary* locs();
   virtual intptr_t DeoptimizationTarget() const;
   virtual Representation RequiredInputRepresentation(intptr_t i) const;
 
-  // Replace the comparison with another, leaving the branch intact.
+  // A misleadingly named function for use in template functions that also
+  // replace definitions.  In this case, leave the branch intact and replace
+  // its comparison with another comparison that has been removed from the
+  // graph but still has uses properly linked into their definition's use
+  // list.
   void ReplaceWith(ComparisonInstr* other,
-                   ForwardInstructionIterator* ignored) {
-    comparison_ = other;
-  }
+                   ForwardInstructionIterator* ignored);
 
   virtual Instruction* Canonicalize(FlowGraphOptimizer* optimizer);
 
   virtual void PrintTo(BufferFormatter* f) const;
 
  private:
   ComparisonInstr* comparison_;
   const bool is_checked_;
 
   DISALLOW_COPY_AND_ASSIGN(BranchInstr);
@@ skipping 2784 matching lines @@
   ForwardInstructionIterator* current_iterator_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(FlowGraphVisitor);
 };
 
 
 }  // namespace dart
 
 #endif  // VM_INTERMEDIATE_LANGUAGE_H_