Add OptimizingCompilerStats to the CodeGenerator class.

Just refactoring, not yet used, but will be used by the incoming patch
series and future CodeGen specific stats.

Change-Id: I7d20489907b82678120518a77bdab9c4cc58f937
Signed-off-by: Serban Constantinescu <serban.constantinescu@linaro.org>
diff --git a/compiler/optimizing/code_generator_mips64.h b/compiler/optimizing/code_generator_mips64.h
index ae7c568..6d4fac3 100644
--- a/compiler/optimizing/code_generator_mips64.h
+++ b/compiler/optimizing/code_generator_mips64.h
@@ -220,7 +220,8 @@
  public:
   CodeGeneratorMIPS64(HGraph* graph,
                       const Mips64InstructionSetFeatures& isa_features,
-                      const CompilerOptions& compiler_options);
+                      const CompilerOptions& compiler_options,
+                      OptimizingCompilerStats* stats = nullptr);
   virtual ~CodeGeneratorMIPS64() {}
 
   void GenerateFrameEntry() OVERRIDE;