Clean up NullCheck generation and record stats about it.

This removes redundant code from the generators and allows for easier
stat recording.

Change-Id: Iccd4368f9e9d87a6fecb863dee4e2145c97851c4
diff --git a/compiler/optimizing/code_generator_x86.h b/compiler/optimizing/code_generator_x86.h
index 0795f3b..c397899 100644
--- a/compiler/optimizing/code_generator_x86.h
+++ b/compiler/optimizing/code_generator_x86.h
@@ -271,8 +271,6 @@
   void PushOntoFPStack(Location source, uint32_t temp_offset,
                        uint32_t stack_adjustment, bool is_fp, bool is_wide);
 
-  void GenerateImplicitNullCheck(HNullCheck* instruction);
-  void GenerateExplicitNullCheck(HNullCheck* instruction);
   template<class LabelType>
   void GenerateTestAndBranch(HInstruction* instruction,
                              size_t condition_input_index,
@@ -541,6 +539,8 @@
   }
 
   void GenerateNop();
+  void GenerateImplicitNullCheck(HNullCheck* instruction);
+  void GenerateExplicitNullCheck(HNullCheck* instruction);
 
  private:
   // Factored implementation of GenerateFieldLoadWithBakerReadBarrier