dart2js cps: Fix bug in trampoline visitor.

pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart

Index: pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart
diff --git a/pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart b/pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart
index 1df27b6739fb4e551e378f0aa142018eb6f18a1e..9c56c480ae815a023748b54acf05c05ec7d02c53 100644
--- a/pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart
+++ b/pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart
@@ -2067,7 +2067,9 @@ class TrampolineRecursiveVisitor extends DeepRecursiveVisitor {
     if (cont.isReturnContinuation) {
       traverseContinuation(cont);
     } else {
-      _trampoline(traverseContinuation(cont));
+      int initialHeight = _stack.length;
+      Expression body = traverseContinuation(cont);
+      _trampoline(body, initialHeight: initialHeight);
     }
   }
 
@@ -2107,8 +2109,8 @@ class TrampolineRecursiveVisitor extends DeepRecursiveVisitor {
     return node.body;
   }
 
-  void _trampoline(Expression node) {
-    int initialHeight = _stack.length;
+  void _trampoline(Expression node, {int initialHeight}) {
+    initialHeight = initialHeight ?? _stack.length;
     _processBlock(node);
     while (_stack.length > initialHeight) {
       StackAction callback = _stack.removeLast();