- Roll engine to version 9867298f86a7ccd5f1c07a83796ee21567d37fb0

- Remove redundant strong flag as it is the default for preview-dart-2
now

bin/internal/engine.version

-0f3a8cef60bfe20afeaebe2945087cec90c65369
+9867298f86a7ccd5f1c07a83796ee21567d37fb0

packages/flutter_tools/lib/src/android/android_device.dart

@@ -388,7 +388,6 @@ class AndroidDevice extends Device {
       return new LaunchResult.failed();
 
     final bool traceStartup = platformArgs['trace-startup'] ?? false;
-    final bool strongMode = platformArgs['strong'] ?? false;
     final AndroidApk apk = package;
     printTrace('$this startApp');
 
@@ -417,9 +416,6 @@ class AndroidDevice extends Device {
 
     if (traceStartup)
       cmd.addAll(<String>['--ez', 'trace-startup', 'true']);
-    if (strongMode) {
-      cmd.addAll(<String>['--ez', 'strong', 'true']);
-    }
     if (route != null)
       cmd.addAll(<String>['--es', 'route', route]);
     if (debuggingOptions.enableSoftwareRendering)

packages/flutter_tools/lib/src/android/gradle.dart

@@ -299,7 +299,6 @@ Future<Null> _buildGradleProjectV2(String gradle, BuildInfo buildInfo, String ta
   }
   if (buildInfo.previewDart2) {
     command.add('-Ppreview-dart-2=true');
-    command.add('-Pstrong=true');
     if (buildInfo.trackWidgetCreation)
       command.add('-Ptrack-widget-creation=true');
     if (buildInfo.extraFrontEndOptions != null)

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

@@ -348,7 +348,6 @@ class AppDomain extends Domain {
     DebuggingOptions options, bool enableHotReload, {
     String applicationBinary,
     bool previewDart2: false,
-    bool strongMode: false,
     String projectRootPath,
     String packagesFilePath,
     String projectAssets,

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

@@ -110,10 +110,6 @@ class RunCommand extends RunCommandBase {
     argParser.addFlag('preview-dart-2',
         hide: !verboseHelp,
         help: 'Preview Dart 2.0 functionality.');
-    argParser.addFlag('strong',
-        hide: !verboseHelp,
-        help: 'Turn on strong mode semantics.\n'
-              'Valid only when --preview-dart-2 is also specified');
     argParser.addFlag('track-widget-creation',
         hide: !verboseHelp,
         help: 'Track widget creation locations. Requires Dart 2.0 functionality.');

packages/flutter_tools/lib/src/ios/devices.dart

@@ -190,14 +190,9 @@ class IOSDevice extends Device {
       return new LaunchResult.failed();
     }
 
-    final bool strongMode = platformArgs['strong'] ?? false;
-
     // Step 3: Attempt to install the application on the device.
     final List<String> launchArguments = <String>['--enable-dart-profiling'];
 
-    if (strongMode)
-      launchArguments.add('--strong');
-
     if (debuggingOptions.startPaused)
       launchArguments.add('--start-paused');
 

packages/flutter_tools/lib/src/ios/simulators.dart

@@ -316,14 +316,9 @@ class IOSSimulator extends Device {
         return new LaunchResult.failed();
     }
 
-    final bool strongMode = platformArgs['strong'] ?? false;
-
     // Prepare launch arguments.
     final List<String> args = <String>['--enable-dart-profiling'];
 
-    if (strongMode)
-      args.add('--strong');
-
     if (!prebuiltApplication) {
       args.addAll(<String>[
         '--flutter-assets-dir=${fs.path.absolute(getAssetBuildDirectory())}',

packages/flutter_tools/lib/src/resident_runner.dart

@@ -274,8 +274,6 @@ class FlutterDevice {
     }
 
     final Map<String, dynamic> platformArgs = <String, dynamic>{};
-    if (hotRunner.previewDart2 != null)
-      platformArgs['strong'] = hotRunner.previewDart2;
 
     startEchoingDeviceLog();
 
@@ -337,8 +335,6 @@ class FlutterDevice {
     final Map<String, dynamic> platformArgs = <String, dynamic>{};
     if (coldRunner.traceStartup != null)
       platformArgs['trace-startup'] = coldRunner.traceStartup;
-    if (coldRunner.previewDart2 != null)
-      platformArgs['strong'] = coldRunner.previewDart2;
 
     startEchoingDeviceLog();
 

packages/flutter_tools/lib/src/test/flutter_platform.dart

@@ -201,7 +201,6 @@ class _FlutterPlatform extends PlatformPlugin {
 
       String mainDart = listenerFile.path;
       String bundlePath;
-      bool strongMode = false;
 
       if (previewDart2) {
         mainDart = await compile(
@@ -236,7 +235,6 @@ class _FlutterPlatform extends PlatformPlugin {
         }
 
         bundlePath = tempBundleDirectory.path;
-        strongMode = true;
       }
 
       final Process process = await _startProcess(
@@ -246,7 +244,6 @@ class _FlutterPlatform extends PlatformPlugin {
         enableObservatory: enableObservatory,
         startPaused: startPaused,
         bundlePath: bundlePath,
-        strongMode: strongMode,
         observatoryPort: explicitObservatoryPort,
       );
       subprocessActive = true;
@@ -521,7 +518,6 @@ void main() {
     String bundlePath,
     bool enableObservatory: false,
     bool startPaused: false,
-    bool strongMode: false,
     int observatoryPort,
   }) {
     assert(executable != null); // Please provide the path to the shell in the SKY_SHELL environment variable.
@@ -549,11 +545,7 @@ void main() {
     if (bundlePath != null) {
       command.add('--flutter-assets-dir=$bundlePath');
     }
-    if (strongMode) {
-      command.add('--strong');
-    } else {
     command.add('--enable-checked-mode');
-    }
     command.addAll(<String>[
       '--enable-dart-profiling',
       '--non-interactive',