Guard more thoroughly against stack overflows in the backtracking version solver.

sdk/lib/_internal/pub/lib/src/solver/backtracking_solver.dart

Index: sdk/lib/_internal/pub/lib/src/solver/backtracking_solver.dart
diff --git a/sdk/lib/_internal/pub/lib/src/solver/backtracking_solver.dart b/sdk/lib/_internal/pub/lib/src/solver/backtracking_solver.dart
index a5e3e3c5b4ea4a8df3dc16dc121b7e7146601af5..73af43e78e533b4ac3bf042deb868f12972b5ffa 100644
--- a/sdk/lib/_internal/pub/lib/src/solver/backtracking_solver.dart
+++ b/sdk/lib/_internal/pub/lib/src/solver/backtracking_solver.dart
@@ -168,7 +168,7 @@ class BacktrackingSolver {
   /// version of it. If there are no more versions, continues to backtrack to
   /// previous selections, and so on. If there is nothing left to backtrack to,
   /// completes to the last failure that occurred.
-  Future<List<PackageId>> _traverseSolution() {
+  Future<List<PackageId>> _traverseSolution() => resetStack(() {
     return new Traverser(this).traverse().catchError((error) {
       if (error is! SolveFailure) throw error;
 
@@ -180,7 +180,7 @@ class BacktrackingSolver {
       // All out of solutions, so fail.
       throw error;
     });
-  }
+  });
 
   /// Backtracks from the current failed solution and determines the next
   /// solution to try. If possible, it will backjump based on the cause of the
@@ -408,9 +408,7 @@ class Traverser {
     // Move onto the next package if we've traversed all of these references.
     if (refs.isEmpty) return _traversePackage();
 
-    // Pump the event loop to flatten the stack trace and workaround #9583.
-    // If that bug is fixed, this can be Future.sync() instead.
-    return new Future(() {
+    return resetStack(() {
       var ref = refs.removeFirst();
 
       _validateDependency(ref, depender);