Improve resolved classes saving strategy

If we already have a non empty profile file it means that we already
saved once the resolved classes. So there's no need to hurry up and
start the profile saver eagerly after 2s.

Bug: 27600652

(cherry picked from commit c15e566b36170237f01ccefc12129c1578a02140)

Change-Id: Iecc730c25eab779efccbbde66432dbbc61192e8a
diff --git a/runtime/utils.h b/runtime/utils.h
index 83ac0b8..c1e88a4 100644
--- a/runtime/utils.h
+++ b/runtime/utils.h
@@ -296,6 +296,7 @@
 
 // Returns true if the file exists.
 bool FileExists(const std::string& filename);
+bool FileExistsAndNotEmpty(const std::string& filename);
 
 class VoidFunctor {
  public: