Revert "Roll engine after dart roll (#12473)" (#12477)

This reverts commit e7061698.

This causes preview-dart-2 test failures.

bin/internal/engine.version

-74e58f66d492a28a2c47ac5402d0b8b8a740cf62
+459f722b86415da01386fe41f37bafa842f11ae8

packages/flutter/lib/src/cupertino/route.dart

@@ -88,9 +88,8 @@ class CupertinoPageRoute<T> extends PageRoute<T> {
        assert(settings != null),
        assert(maintainState != null),
        assert(fullscreenDialog != null),
-       super(settings: settings, fullscreenDialog: fullscreenDialog) {
-    assert(opaque); // PageRoute makes it return true.
-  }
+       assert(opaque), // PageRoute makes it return true.
+       super(settings: settings, fullscreenDialog: fullscreenDialog);
 
   /// Builds the primary contents of the route.
   final WidgetBuilder builder;

packages/flutter/lib/src/foundation/assertions.dart

@@ -329,7 +329,7 @@ class FlutterError extends AssertionError {
       '_FakeAsync',
       '_FrameCallbackEntry',
     ];
-    final RegExp stackParser = new RegExp(r'^#[0-9]+ +([^.]+).* \(([^/]*)/.+:[0-9]+(?::[0-9]+)?\)$');
+    final RegExp stackParser = new RegExp(r'^#[0-9]+ +([^.]+).* \(([^/]*)/[^:]+:[0-9]+(?::[0-9]+)?\)$');
     final RegExp packageParser = new RegExp(r'^([^:]+):(.+)$');
     final List<String> result = <String>[];
     final List<String> skipped = <String>[];

packages/flutter/lib/src/material/page.dart

@@ -70,9 +70,8 @@ class MaterialPageRoute<T> extends PageRoute<T> {
     this.maintainState: true,
     bool fullscreenDialog: false,
   }) : assert(builder != null),
-       super(settings: settings, fullscreenDialog: fullscreenDialog) {
-    assert(opaque);
-  }
+       assert(opaque),
+       super(settings: settings, fullscreenDialog: fullscreenDialog);
 
   /// Builds the primary contents of the route.
   final WidgetBuilder builder;

packages/flutter/lib/src/widgets/pages.dart

@@ -81,11 +81,10 @@ class PageRouteBuilder<T> extends PageRoute<T> {
     this.maintainState: true,
   }) : assert(pageBuilder != null),
        assert(transitionsBuilder != null),
+       assert(opaque != null),
        assert(barrierDismissible != null),
        assert(maintainState != null),
-       super(settings: settings) {
-    assert(opaque != null);
-  }
+       super(settings: settings);
 
   /// Used build the route's primary contents.
   ///