Address frame policy benchmark flakes (flutter#155130)

Recently the microbenchmarks were flakey, but from an older bug. Turns out, `LiveTestWidgetsFlutterBindingFramePolicy` is defaulted to `fadePointers` with this fun note:

> This can result in additional frames being pumped beyond those that
the test itself requests, which can cause differences in behavior

Both `text_intrinsic_bench` and `build_bench` use a similar pattern:
* Load stocks app
* Open the menu
* Switch to `benchmark` frame policy

What happens, rarely, is that
`LiveTestWidgetsFlutterBinding.pumpBenchmark()` will call (async) `handleBeginFrame` and `handleDrawFrame`. `handleDrawFrame` juggles a tri-state boolean (null, false, true). This boolean is only reset to `null` when handleDrawFrame is called back to back, say, from an extra frame that was scheduled.

1. Switch tri-state boolean to an enum, its easier to read
2. remove asserts that compile away in benchmarks (`--profile`)
3. use `Error.throwWithStackTrace` to keep stack traces.

I've been running this test on device lab hardware for hundreds of runs and have not hit a failure yet.

Fixes flutter#150542
Fixes flutter#150543 - throw stack!

Author: jtmcdole

dev/benchmarks/microbenchmarks/lib/layout/text_intrinsic_bench.dart

@@ -33,7 +33,7 @@ Future<void> execute() async {
   await benchmarkWidgets((WidgetTester tester) async {
     runApp(intrinsicTextHeight);
     // Wait for the UI to stabilize.
-    await tester.pump(const Duration(seconds: 1));
+    await tester.pumpAndSettle(const Duration(seconds: 1));
 
     final TestViewConfiguration big = TestViewConfiguration.fromView(
       size: const Size(360.0, 640.0),

dev/benchmarks/microbenchmarks/lib/stocks/build_bench.dart

@@ -29,7 +29,7 @@ Future<List<double>> runBuildBenchmark() async {
     await tester.pump(const Duration(seconds: 1)); // Complete startup animation
     await tester.tapAt(const Offset(20.0, 40.0)); // Open drawer
     await tester.pump(); // Start drawer animation
-    await tester.pump(const Duration(seconds: 1)); // Complete drawer animation
+    await tester.pumpAndSettle(const Duration(seconds: 1)); // Complete drawer animation
 
     final Element appState = tester.element(find.byType(stocks.StocksApp));
     binding.framePolicy = LiveTestWidgetsFlutterBindingFramePolicy.benchmark;

packages/flutter_test/lib/src/binding.dart

@@ -1649,6 +1649,12 @@ enum LiveTestWidgetsFlutterBindingFramePolicy {
   benchmarkLive,
 }
 
+enum _HandleDrawFrame {
+  reset,
+  drawFrame,
+  skipFrame,
+}
+
 /// A variant of [TestWidgetsFlutterBinding] for executing tests
 /// on a device, typically via `flutter run`, or via integration tests.
 /// This is intended to allow interactive test development.
@@ -1779,31 +1785,35 @@ class LiveTestWidgetsFlutterBinding extends TestWidgetsFlutterBinding {
     return super.reassembleApplication();
   }
 
-  bool? _doDrawThisFrame;
+  _HandleDrawFrame _drawFrame = _HandleDrawFrame.reset;
 
   @override
   void handleBeginFrame(Duration? rawTimeStamp) {
-    assert(_doDrawThisFrame == null);
+    if (_drawFrame != _HandleDrawFrame.reset) {
+      throw StateError('handleBeginFrame() called before previous handleDrawFrame()');
+    }
     if (_expectingFrame ||
         _expectingFrameToReassemble ||
         (framePolicy == LiveTestWidgetsFlutterBindingFramePolicy.fullyLive) ||
         (framePolicy == LiveTestWidgetsFlutterBindingFramePolicy.benchmarkLive) ||
         (framePolicy == LiveTestWidgetsFlutterBindingFramePolicy.benchmark) ||
         (framePolicy == LiveTestWidgetsFlutterBindingFramePolicy.fadePointers && _viewNeedsPaint)) {
-      _doDrawThisFrame = true;
+      _drawFrame = _HandleDrawFrame.drawFrame;
       super.handleBeginFrame(rawTimeStamp);
     } else {
-      _doDrawThisFrame = false;
+      _drawFrame = _HandleDrawFrame.skipFrame;
     }
   }
 
   @override
   void handleDrawFrame() {
-    assert(_doDrawThisFrame != null);
-    if (_doDrawThisFrame!) {
+    if (_drawFrame == _HandleDrawFrame.reset) {
+      throw StateError('handleDrawFrame() called without paired handleBeginFrame()');
+    }
+    if (_drawFrame == _HandleDrawFrame.drawFrame) {
       super.handleDrawFrame();
     }
-    _doDrawThisFrame = null;
+    _drawFrame = _HandleDrawFrame.reset;
     _viewNeedsPaint = false;
     _expectingFrameToReassemble = false;
     if (_expectingFrame) { // set during pump

packages/flutter_test/lib/src/widget_tester.dart

@@ -683,15 +683,19 @@ class WidgetTester extends WidgetController implements HitTestDispatcher, Ticker
     }());
 
     dynamic caughtException;
-    void handleError(dynamic error, StackTrace stackTrace) => caughtException ??= error;
+    StackTrace? stackTrace;
+    void handleError(dynamic error, StackTrace trace)  {
+      caughtException ??= error;
+      stackTrace ??= trace;
+    }
 
     await Future<void>.microtask(() { binding.handleBeginFrame(duration); }).catchError(handleError);
     await idle();
     await Future<void>.microtask(() { binding.handleDrawFrame(); }).catchError(handleError);
     await idle();
 
     if (caughtException != null) {
-      throw caughtException as Object; // ignore: only_throw_errors, rethrowing caught exception.
+      Error.throwWithStackTrace(caughtException as Object, stackTrace!);
     }
   }