ART: Make ProcessStrings less noisy

Only print statistics in debug mode or when verbose-logging.

Bug: 19082662
Change-Id: Ibc1d336a5abe7a05fb37e8d3a9b9c9c8131e5bbc
diff --git a/compiler/image_writer.cc b/compiler/image_writer.cc
index 8c7d611..dfebd3e 100644
--- a/compiler/image_writer.cc
+++ b/compiler/image_writer.cc
@@ -561,8 +561,10 @@
   }
   CHECK_EQ(pos, num_chars);
 
-  LOG(INFO) << "Total # image strings=" << total_strings << " combined length="
-      << num_chars << " prefix saved chars=" << prefix_saved_chars;
+  if (kIsDebugBuild || VLOG_IS_ON(compiler)) {
+    LOG(INFO) << "Total # image strings=" << total_strings << " combined length="
+        << num_chars << " prefix saved chars=" << prefix_saved_chars;
+  }
   ComputeEagerResolvedStrings();
 }