Revert "Add stats support for existing optimizations"

Breaks the build. Please ensure your changes build.

This reverts commit 06241b1b07fb031b7d2cf55f4b78d3444d07cc2d.

Change-Id: I68b18f99a9882719bf6654d3313531a7965b8483
diff --git a/compiler/optimizing/constant_folding.h b/compiler/optimizing/constant_folding.h
index df89371..2698b2d 100644
--- a/compiler/optimizing/constant_folding.h
+++ b/compiler/optimizing/constant_folding.h
@@ -32,10 +32,8 @@
  */
 class HConstantFolding : public HOptimization {
  public:
-  HConstantFolding(HGraph* graph,
-                   OptimizingCompilerStats* stats,
-                   const char* name = kConstantFoldingPassName)
-      : HOptimization(graph, name, stats) {}
+  explicit HConstantFolding(HGraph* graph, const char* name = kConstantFoldingPassName)
+      : HOptimization(graph, name) {}
 
   void Run() OVERRIDE;