optimizing: Refactor statistics to use OptimizingCompilerStats helper

Remove all copies of 'MaybeRecordStat', replacing them with a single
OptimizingCompilerStats::MaybeRecordStat helper.

Change-Id: I83b96b41439dccece3eee2e159b18c95336ea933
diff --git a/compiler/optimizing/intrinsics.cc b/compiler/optimizing/intrinsics.cc
index 7bdeef5..11725f4 100644
--- a/compiler/optimizing/intrinsics.cc
+++ b/compiler/optimizing/intrinsics.cc
@@ -154,7 +154,8 @@
                                  NeedsEnvironmentOrCache(intrinsic),
                                  GetSideEffects(intrinsic),
                                  GetExceptions(intrinsic));
-            MaybeRecordStat(MethodCompilationStat::kIntrinsicRecognized);
+            MaybeRecordStat(stats_,
+                            MethodCompilationStat::kIntrinsicRecognized);
           }
         }
       }