[flutter_tools] Reland fast start by default for Android (flutter#49315)

Author: Jonah Williams

dev/devicelab/bin/tasks/commands_test.dart

@@ -26,7 +26,7 @@ void main() {
       print('run: starting...');
       final Process run = await startProcess(
         path.join(flutterDirectory.path, 'bin', 'flutter'),
-        <String>['run', '--verbose', '--disable-service-auth-codes', '-d', device.deviceId, 'lib/commands.dart'],
+        <String>['run', '--verbose', '--disable-service-auth-codes', '--no-fast-start', '-d', device.deviceId, 'lib/commands.dart'],
       );
       final StreamController<String> stdout = StreamController<String>.broadcast();
       run.stdout

dev/devicelab/bin/tasks/named_isolates_test.dart

@@ -26,7 +26,7 @@ void main() {
     Completer<void> firstNameFound = Completer<void>();
     Completer<void> secondNameFound = Completer<void>();
     final Process runProcess = await _run(device: device, command:
-        <String>['run', '--disable-service-auth-codes'], stdoutListener: (String line) {
+        <String>['run', '--disable-service-auth-codes', '--no-fast-start'], stdoutListener: (String line) {
       if (line.contains(_kFirstIsolateName)) {
         firstNameFound.complete();
       } else if (line.contains(_kSecondIsolateName)) {

dev/devicelab/bin/tasks/run_machine_concurrent_hot_reload.dart

@@ -48,6 +48,7 @@ void main() {
           'run',
           '--machine',
           '--verbose',
+          '--no-fast-start',
           '-d',
           device.deviceId,
           'lib/commands.dart',

dev/devicelab/bin/tasks/service_extensions_test.dart

@@ -25,7 +25,7 @@ void main() {
       print('run: starting...');
       final Process run = await startProcess(
         path.join(flutterDirectory.path, 'bin', 'flutter'),
-        <String>['run', '--verbose', '--disable-service-auth-codes', '-d', device.deviceId, 'lib/main.dart'],
+        <String>['run', '--verbose', '--no-fast-start', '--disable-service-auth-codes', '-d', device.deviceId, 'lib/main.dart'],
       );
       run.stdout
           .transform<String>(utf8.decoder)

dev/devicelab/lib/tasks/perf_tests.dart

@@ -719,6 +719,7 @@ class ReportedDurationTest {
       print('launching $project$test on device...');
       await flutter('run', options: <String>[
         '--verbose',
+        '--no-fast-start',
         '--${_reportedDurationTestToString(flavor)}',
         '--no-resident',
         '-d', device.deviceId,

packages/flutter_tools/lib/src/commands/run.dart

@@ -189,8 +189,7 @@ class RunCommand extends RunCommandBase {
       )
       ..addFlag('fast-start',
         negatable: true,
-        defaultsTo: false,
-        hide: true,
+        defaultsTo: true,
         help: 'Whether to quickly bootstrap applications with a minimal app. '
               'Currently this is only supported on Android devices. This option '
               'cannot be paired with --use-application-binary.'
@@ -319,10 +318,6 @@ class RunCommand extends RunCommandBase {
       await super.validateCommand();
     }
 
-    if (boolArg('fast-start') && runningWithPrebuiltApplication) {
-      throwToolExit('--fast-start is not supported with --use-application-binary');
-    }
-
     devices = await findAllTargetDevices();
     if (devices == null) {
       throwToolExit(null);
@@ -365,7 +360,9 @@ class RunCommand extends RunCommandBase {
         vmserviceOutFile: stringArg('vmservice-out-file'),
         // Allow forcing fast-start to off to prevent doing more work on devices that
         // don't support it.
-        fastStart: boolArg('fast-start') && devices.every((Device device) => device.supportsFastStart),
+        fastStart: boolArg('fast-start')
+          && !runningWithPrebuiltApplication
+          && devices.every((Device device) => device.supportsFastStart),
       );
     }
   }
@@ -428,12 +425,6 @@ class RunCommand extends RunCommandBase {
     }
 
     for (final Device device in devices) {
-      if (!device.supportsFastStart && boolArg('fast-start')) {
-        globals.printStatus(
-          'Using --fast-start option with device ${device.name}, but this device '
-          'does not support it. Overriding the setting to false.'
-        );
-      }
       if (await device.isLocalEmulator) {
         if (await device.supportsHardwareRendering) {
           final bool enableSoftwareRendering = boolArg('enable-software-rendering') == true;

packages/flutter_tools/test/commands.shard/hermetic/run_test.dart

@@ -77,7 +77,7 @@ void main() {
         ]);
         fail('Expect exception');
       } catch (e) {
-        expect(e.toString(), contains('--fast-start is not supported with --use-application-binary'));
+        expect(e.toString(), isNot(contains('--fast-start is not supported with --use-application-binary')));
       }
     }, overrides: <Type, Generator>{
       FileSystem: () => MemoryFileSystem(),
@@ -115,10 +115,10 @@ void main() {
       }
 
       final BufferLogger bufferLogger = globals.logger as BufferLogger;
-      expect(bufferLogger.statusText, contains(
+      expect(bufferLogger.statusText, isNot(contains(
         'Using --fast-start option with device mockdevice, but this device '
         'does not support it. Overriding the setting to false.'
-      ));
+      )));
     }, overrides: <Type, Generator>{
       FileSystem: () => MemoryFileSystem(),
       ProcessManager: () => FakeProcessManager.any(),