Use --dump-stats to dump optimizing compiler stats.

VLOG(compiler) produces too much output and it takes a long time if you
only need to see how an analysis performs.

Change-Id: Ic17c2b2b5fec431d356cecd37289fb96985d4d7f
diff --git a/compiler/driver/compiler_driver.h b/compiler/driver/compiler_driver.h
index bd9d7c1..95534fb 100644
--- a/compiler/driver/compiler_driver.h
+++ b/compiler/driver/compiler_driver.h
@@ -398,6 +398,10 @@
     return thread_count_;
   }
 
+  bool GetDumpStats() const {
+    return dump_stats_;
+  }
+
   bool GetDumpPasses() const {
     return dump_passes_;
   }