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/licm.cc b/compiler/optimizing/licm.cc
index f0086fb..10524b0 100644
--- a/compiler/optimizing/licm.cc
+++ b/compiler/optimizing/licm.cc
@@ -141,7 +141,7 @@
             DCHECK(!instruction->HasEnvironment());
           }
           instruction->MoveBefore(pre_header->GetLastInstruction());
-          MaybeRecordStat(MethodCompilationStat::kLoopInvariantMoved);
+          MaybeRecordStat(stats_, MethodCompilationStat::kLoopInvariantMoved);
         } else if (instruction->CanThrow() || instruction->DoesAnyWrite()) {
           // If `instruction` can do something visible (throw or write),
           // we cannot move further instructions that can throw.