Add default value to isBreakTarget optional parameter.

pkg/compiler/lib/src/kernel/kernel_visitor.dart

Index: pkg/compiler/lib/src/kernel/kernel_visitor.dart
diff --git a/pkg/compiler/lib/src/kernel/kernel_visitor.dart b/pkg/compiler/lib/src/kernel/kernel_visitor.dart
index 5216b97d1aff5b97eb2646398b6bcead25870333..03f700241ce68d3b4e63067a08aa2080767633e3 100644
--- a/pkg/compiler/lib/src/kernel/kernel_visitor.dart
+++ b/pkg/compiler/lib/src/kernel/kernel_visitor.dart
@@ -405,7 +405,7 @@ class KernelVisitor extends Object
   /// JumpTargets don't know about it.
   ir.Statement buildBreakTarget(
       ir.Statement statement, Node node, JumpTarget jumpTarget,
-      [bool isBreakTarget]) {
+      [bool isBreakTarget = false]) {
     assert(node.isValidBreakTarget());
     assert(jumpTarget == elements.getTargetDefinition(node));
     associateNode(statement, node);