Add file missing from earlier commit

src/app/statistics_reporter.rs

@@ -0,0 +1,31 @@
+use log::info;
+
+pub struct StatisticsReporter {
+    total_time_seconds: f64,
+    frame_count: u32,
+}
+
+impl StatisticsReporter {
+    pub fn new() -> Self {
+        let total_time_seconds = 0.0;
+        let frame_count = 0;
+        Self {
+            total_time_seconds,
+            frame_count,
+        }
+    }
+
+    pub fn log_frame_time_seconds(&mut self, t: f64) {
+        self.total_time_seconds += t;
+        self.frame_count += 1;
+        if self.total_time_seconds >= 1.0 {
+            info!(
+                "Average frame time: {:.0} ms ({:.1} fps)",
+                self.total_time_seconds * 1000.0 / (self.frame_count as f64),
+                (self.frame_count as f64) / self.total_time_seconds
+            );
+            self.total_time_seconds = 0.0;
+            self.frame_count = 0;
+        }
+    }
+}