Have HInstruction::StrictlyDominates compute strict dominance.

Change-Id: I3a4fa133268615fb4ce54a0bcb43e0c2458cc865
diff --git a/compiler/optimizing/nodes.h b/compiler/optimizing/nodes.h
index ec26c4a..7bb71b6 100644
--- a/compiler/optimizing/nodes.h
+++ b/compiler/optimizing/nodes.h
@@ -684,9 +684,10 @@
     return result;
   }
 
-  // Does this instruction dominate `other_instruction`?  Aborts if
-  // this instruction and `other_instruction` are both phis.
-  bool Dominates(HInstruction* other_instruction) const;
+  // Does this instruction strictly dominate `other_instruction`?
+  // Returns false if this instruction and `other_instruction` are the same.
+  // Aborts if this instruction and `other_instruction` are both phis.
+  bool StrictlyDominates(HInstruction* other_instruction) const;
 
   int GetId() const { return id_; }
   void SetId(int id) { id_ = id; }