Opt into deterministic snapshots.

Also, remove old flags.
diff --git a/packages/flutter_tools/lib/src/base/build.dart b/packages/flutter_tools/lib/src/base/build.dart
index 185ecc5..757a8cf 100644
--- a/packages/flutter_tools/lib/src/base/build.dart
+++ b/packages/flutter_tools/lib/src/base/build.dart
@@ -122,14 +122,8 @@
 
     final String depfilePath = fs.path.join(outputDir.path, 'snapshot.d');
     final List<String> genSnapshotArgs = <String>[
-      '--url_mapping=dart:ui,$uiPath',
-      '--url_mapping=dart:vmservice_io,$vmServicePath',
+      '--deterministic',
     ];
-    genSnapshotArgs.addAll(<String>[
-      '--reify-generic-functions',
-      '--strong',
-      '--sync-async',
-    ]);
     if (extraGenSnapshotOptions != null && extraGenSnapshotOptions.isNotEmpty) {
       printTrace('Extra gen_snapshot options: $extraGenSnapshotOptions');
       genSnapshotArgs.addAll(extraGenSnapshotOptions);
@@ -379,9 +373,7 @@
 
     final String depfilePath = fs.path.join(outputDir.path, 'snapshot.d');
     final List<String> genSnapshotArgs = <String>[
-      '--reify-generic-functions',
-      '--strong',
-      '--sync-async',
+      '--deterministic',
     ];
     if (buildMode == BuildMode.debug) {
       genSnapshotArgs.add('--enable_asserts');
diff --git a/packages/flutter_tools/test/base/build_test.dart b/packages/flutter_tools/test/base/build_test.dart
index 8fb6f23..467e5d7 100644
--- a/packages/flutter_tools/test/base/build_test.dart
+++ b/packages/flutter_tools/test/base/build_test.dart
@@ -191,11 +191,7 @@
       expect(genSnapshot.snapshotType.mode, BuildMode.profile);
       expect(genSnapshot.packagesPath, '.packages');
       expect(genSnapshot.additionalArgs, <String>[
-        '--url_mapping=dart:ui,${fs.path.join(skyEnginePath, 'lib', 'ui', 'ui.dart')}',
-        '--url_mapping=dart:vmservice_io,${fs.path.join(skyEnginePath, 'sdk_ext', 'vmservice_io.dart')}',
-        '--reify-generic-functions',
-        '--strong',
-        '--sync-async',
+        '--deterministic',
         '--snapshot_kind=app-aot-assembly',
         '--assembly=${fs.path.join(outputPath, 'snapshot_assembly.S')}',
         '--no-sim-use-hardfp',
@@ -234,11 +230,7 @@
       expect(genSnapshot.snapshotType.mode, BuildMode.profile);
       expect(genSnapshot.packagesPath, '.packages');
       expect(genSnapshot.additionalArgs, <String>[
-        '--url_mapping=dart:ui,${fs.path.join(skyEnginePath, 'lib', 'ui', 'ui.dart')}',
-        '--url_mapping=dart:vmservice_io,${fs.path.join(skyEnginePath, 'sdk_ext', 'vmservice_io.dart')}',
-        '--reify-generic-functions',
-        '--strong',
-        '--sync-async',
+        '--deterministic',
         '--snapshot_kind=app-aot-assembly',
         '--assembly=${fs.path.join(outputPath, 'snapshot_assembly.S')}',
         'main.dill',
@@ -277,11 +269,7 @@
       expect(genSnapshot.snapshotType.mode, BuildMode.profile);
       expect(genSnapshot.packagesPath, '.packages');
       expect(genSnapshot.additionalArgs, <String>[
-        '--url_mapping=dart:ui,${fs.path.join(skyEnginePath, 'lib', 'ui', 'ui.dart')}',
-        '--url_mapping=dart:vmservice_io,${fs.path.join(skyEnginePath, 'sdk_ext', 'vmservice_io.dart')}',
-        '--reify-generic-functions',
-        '--strong',
-        '--sync-async',
+        '--deterministic',
         '--snapshot_kind=app-aot-blobs',
         '--vm_snapshot_data=build/foo/vm_snapshot_data',
         '--isolate_snapshot_data=build/foo/isolate_snapshot_data',
@@ -325,11 +313,7 @@
       expect(genSnapshot.snapshotType.mode, BuildMode.profile);
       expect(genSnapshot.packagesPath, '.packages');
       expect(genSnapshot.additionalArgs, <String>[
-        '--url_mapping=dart:ui,${fs.path.join(skyEnginePath, 'lib', 'ui', 'ui.dart')}',
-        '--url_mapping=dart:vmservice_io,${fs.path.join(skyEnginePath, 'sdk_ext', 'vmservice_io.dart')}',
-        '--reify-generic-functions',
-        '--strong',
-        '--sync-async',
+        '--deterministic',
         '--snapshot_kind=app-aot-blobs',
         '--vm_snapshot_data=build/foo/vm_snapshot_data',
         '--isolate_snapshot_data=build/foo/isolate_snapshot_data',
@@ -369,11 +353,7 @@
       expect(genSnapshot.snapshotType.mode, BuildMode.release);
       expect(genSnapshot.packagesPath, '.packages');
       expect(genSnapshot.additionalArgs, <String>[
-        '--url_mapping=dart:ui,${fs.path.join(skyEnginePath, 'lib', 'ui', 'ui.dart')}',
-        '--url_mapping=dart:vmservice_io,${fs.path.join(skyEnginePath, 'sdk_ext', 'vmservice_io.dart')}',
-        '--reify-generic-functions',
-        '--strong',
-        '--sync-async',
+        '--deterministic',
         '--snapshot_kind=app-aot-assembly',
         '--assembly=${fs.path.join(outputPath, 'snapshot_assembly.S')}',
         '--no-sim-use-hardfp',
@@ -412,11 +392,7 @@
       expect(genSnapshot.snapshotType.mode, BuildMode.release);
       expect(genSnapshot.packagesPath, '.packages');
       expect(genSnapshot.additionalArgs, <String>[
-        '--url_mapping=dart:ui,${fs.path.join(skyEnginePath, 'lib', 'ui', 'ui.dart')}',
-        '--url_mapping=dart:vmservice_io,${fs.path.join(skyEnginePath, 'sdk_ext', 'vmservice_io.dart')}',
-        '--reify-generic-functions',
-        '--strong',
-        '--sync-async',
+        '--deterministic',
         '--snapshot_kind=app-aot-assembly',
         '--assembly=${fs.path.join(outputPath, 'snapshot_assembly.S')}',
         'main.dill',
@@ -473,11 +449,7 @@
       expect(genSnapshot.snapshotType.mode, BuildMode.release);
       expect(genSnapshot.packagesPath, '.packages');
       expect(genSnapshot.additionalArgs, <String>[
-        '--url_mapping=dart:ui,${fs.path.join(skyEnginePath, 'lib', 'ui', 'ui.dart')}',
-        '--url_mapping=dart:vmservice_io,${fs.path.join(skyEnginePath, 'sdk_ext', 'vmservice_io.dart')}',
-        '--reify-generic-functions',
-        '--strong',
-        '--sync-async',
+        '--deterministic',
         '--snapshot_kind=app-aot-blobs',
         '--vm_snapshot_data=build/foo/vm_snapshot_data',
         '--isolate_snapshot_data=build/foo/isolate_snapshot_data',
@@ -521,11 +493,7 @@
       expect(genSnapshot.snapshotType.mode, BuildMode.release);
       expect(genSnapshot.packagesPath, '.packages');
       expect(genSnapshot.additionalArgs, <String>[
-        '--url_mapping=dart:ui,${fs.path.join(skyEnginePath, 'lib', 'ui', 'ui.dart')}',
-        '--url_mapping=dart:vmservice_io,${fs.path.join(skyEnginePath, 'sdk_ext', 'vmservice_io.dart')}',
-        '--reify-generic-functions',
-        '--strong',
-        '--sync-async',
+        '--deterministic',
         '--snapshot_kind=app-aot-blobs',
         '--vm_snapshot_data=build/foo/vm_snapshot_data',
         '--isolate_snapshot_data=build/foo/isolate_snapshot_data',
@@ -609,9 +577,7 @@
       expect(genSnapshot.snapshotType.mode, BuildMode.debug);
       expect(genSnapshot.packagesPath, '.packages');
       expect(genSnapshot.additionalArgs, <String>[
-        '--reify-generic-functions',
-        '--strong',
-        '--sync-async',
+        '--deterministic',
         '--enable_asserts',
         '--snapshot_kind=app-jit',
         '--load_compilation_trace=$kTrace',
@@ -652,9 +618,7 @@
       expect(genSnapshot.snapshotType.mode, BuildMode.debug);
       expect(genSnapshot.packagesPath, '.packages');
       expect(genSnapshot.additionalArgs, <String>[
-        '--reify-generic-functions',
-        '--strong',
-        '--sync-async',
+        '--deterministic',
         '--enable_asserts',
         '--snapshot_kind=app-jit',
         '--load_compilation_trace=$kTrace',
@@ -706,9 +670,7 @@
       expect(genSnapshot.snapshotType.mode, BuildMode.profile);
       expect(genSnapshot.packagesPath, '.packages');
       expect(genSnapshot.additionalArgs, <String>[
-        '--reify-generic-functions',
-        '--strong',
-        '--sync-async',
+        '--deterministic',
         '--snapshot_kind=app-jit',
         '--load_compilation_trace=$kTrace',
         '--load_vm_snapshot_data=$kEngineVmSnapshotData',
@@ -748,9 +710,7 @@
       expect(genSnapshot.snapshotType.mode, BuildMode.profile);
       expect(genSnapshot.packagesPath, '.packages');
       expect(genSnapshot.additionalArgs, <String>[
-        '--reify-generic-functions',
-        '--strong',
-        '--sync-async',
+        '--deterministic',
         '--snapshot_kind=app-jit',
         '--load_compilation_trace=$kTrace',
         '--load_vm_snapshot_data=$kEngineVmSnapshotData',
@@ -801,9 +761,7 @@
       expect(genSnapshot.snapshotType.mode, BuildMode.release);
       expect(genSnapshot.packagesPath, '.packages');
       expect(genSnapshot.additionalArgs, <String>[
-        '--reify-generic-functions',
-        '--strong',
-        '--sync-async',
+        '--deterministic',
         '--snapshot_kind=app-jit',
         '--load_compilation_trace=$kTrace',
         '--load_vm_snapshot_data=$kEngineVmSnapshotData',
@@ -843,9 +801,7 @@
       expect(genSnapshot.snapshotType.mode, BuildMode.release);
       expect(genSnapshot.packagesPath, '.packages');
       expect(genSnapshot.additionalArgs, <String>[
-        '--reify-generic-functions',
-        '--strong',
-        '--sync-async',
+        '--deterministic',
         '--snapshot_kind=app-jit',
         '--load_compilation_trace=$kTrace',
         '--load_vm_snapshot_data=$kEngineVmSnapshotData',
@@ -884,9 +840,7 @@
       expect(genSnapshot.snapshotType.mode, BuildMode.release);
       expect(genSnapshot.packagesPath, '.packages');
       expect(genSnapshot.additionalArgs, <String>[
-        '--reify-generic-functions',
-        '--strong',
-        '--sync-async',
+        '--deterministic',
         '--snapshot_kind=app-jit',
         '--load_compilation_trace=$kTrace',
         '--load_vm_snapshot_data=$kEngineVmSnapshotData',