Print frame processing latency to debug log

src/stat_trackers.cpp

@@ -0,0 +1,10 @@
+#include "stat_trackers.h"
+
+namespace stat_trackers {
+
+  boost::format
+  one_digit_after_decimal() {
+    return boost::format("%1$.1f");
+  }
+
+}  // namespace stat_trackers