Remove test flakiness (#13252)

dev/integration_tests/external_ui/android/app/src/main/java/io/flutter/externalui/MainActivity.java

@@ -52,8 +52,11 @@ public class MainActivity extends FlutterActivity {
             producerTimer.scheduleAtFixedRate(new TimerTask() {
               @Override
               public void run() {
-                renderer.drawFrame();
-                framesProduced.incrementAndGet();
+                final long time = System.currentTimeMillis();
+                if (frameRate(framesProduced, startTime, time) < fps) {
+                  renderer.drawFrame();
+                  framesProduced.incrementAndGet();
+                }
               }
             }, 0, 1000 / fps);
             consumerTimer = new Timer();
@@ -78,13 +81,14 @@ public class MainActivity extends FlutterActivity {
             producerTimer.cancel();
             consumerTimer.cancel();
             endTime = System.currentTimeMillis();
+            Log.e("TET", "Stopped at " + endTime);
             result.success(null);
             break;
           case "getProducedFrameRate":
-            result.success(framesProduced.get() * 1000 / (double) (endTime - startTime));
+            result.success(frameRate(framesProduced, startTime, endTime));
             break;
           case "getConsumedFrameRate":
-            result.success(framesConsumed.get() * 1000 / (double) (endTime - startTime));
+            result.success(frameRate(framesConsumed, startTime, endTime));
             break;
           default: result.notImplemented();
         }
@@ -110,6 +114,10 @@ public class MainActivity extends FlutterActivity {
     });
   }
 
+  double frameRate(AtomicInteger frameCounter, long startTime, long endTime) {
+    return frameCounter.get() * 1000 / (double) (endTime - startTime);
+  }
+
   @Override
   protected void onDestroy() {
     if (surface != null) {

dev/integration_tests/external_ui/test_driver/main_test.dart

@@ -55,7 +55,7 @@ Future<Null> main() async {
       final String statsFast = await driver.getText(summary);
       final Match matchFast = statsRegExp.matchAsPrefix(statsFast);
       expect(matchFast, isNotNull);
-      expect(double.parse(matchFast.group(1)), closeTo(flutterFrameRate * 2.0, 10.0));
+      expect(double.parse(matchFast.group(1)), closeTo(flutterFrameRate * 2.0, 5.0));
       expect(double.parse(matchFast.group(2)), closeTo(flutterFrameRate, 10.0));
       expect(int.parse(matchFast.group(3)), 1);
     });