Fix indent.

examples/mine_digger/lib/main.dart

diff --git a/examples/mine_digger/lib/main.dart b/examples/mine_digger/lib/main.dart
index 6d2fb8a..4c78fe3 100644
--- a/examples/mine_digger/lib/main.dart
+++ b/examples/mine_digger/lib/main.dart
@@ -66,10 +66,10 @@
     detectedCount = 0;
     // Initialize matrices.
     cells = new List<List>.generate(rows, (int row) {
-        return new List<bool>.filled(cols, false);
+      return new List<bool>.filled(cols, false);
     });
     uiState = new List<List>.generate(rows, (int row) {
-      return new List<CellState>.filled(cols,  CellState.covered);
+      return new List<CellState>.filled(cols, CellState.covered);
     });
     // Place the mines.
     Random random = new Random();