Don't pass --print_snapshot_sizes in product mode

runtime/bin/gen_snapshot.cc

Index: runtime/bin/gen_snapshot.cc
diff --git a/runtime/bin/gen_snapshot.cc b/runtime/bin/gen_snapshot.cc
index 4c00a1505927a7803e857f651f1e94c1c376a8d5..8e2efdaab3655093c4e0a3934d98c88298902156 100644
--- a/runtime/bin/gen_snapshot.cc
+++ b/runtime/bin/gen_snapshot.cc
@@ -1206,7 +1206,9 @@ int main(int argc, char** argv) {
 
   if (IsSnapshottingForPrecompilation()) {
     vm_options.AddArgument("--precompilation");
+#if !defined(PRODUCT)
     vm_options.AddArgument("--print_snapshot_sizes");
+#endif
 #if TARGET_ARCH_ARM
     // This is for the iPod Touch 5th Generation (and maybe other older devices)
     vm_options.AddArgument("--no-use_integer_division");