Add primitive to create closures and use it for closure conversion

pkg/kernel/lib/text/ast_to_text.dart

Index: pkg/kernel/lib/text/ast_to_text.dart
diff --git a/pkg/kernel/lib/text/ast_to_text.dart b/pkg/kernel/lib/text/ast_to_text.dart
index bb7dd93afa4afd9506fcd6294b6209699a0954d9..bff7058e9118fac3892071a7aaeeb88bafc9f5fb 100644
--- a/pkg/kernel/lib/text/ast_to_text.dart
+++ b/pkg/kernel/lib/text/ast_to_text.dart
@@ -1021,6 +1021,18 @@ class Printer extends Visitor<Null> {
     writeSymbol(')');
   }
 
+  visitClosureCreation(ClosureCreation node) {
+    writeWord('MakeClosure');
+    writeSymbol('<');
+    writeNode(node.functionType);
+    writeSymbol('>');
+    writeSymbol('(');
+    writeWord(node.topLevelFunctionName);
+    writeComma();
+    writeExpression(node.contextVector);
+    writeSymbol(')');
+  }
+
   visitDeferredImport(DeferredImport node) {
     write('import "');
     write('${node.importedLibrary.importUri}');