cps-ir: Implement boolean conversion in and use it to implement '&&', '||', and '?:'.

pkg/compiler/lib/src/tree_ir/tree_ir_nodes.dart

Index: pkg/compiler/lib/src/tree_ir/tree_ir_nodes.dart
diff --git a/pkg/compiler/lib/src/tree_ir/tree_ir_nodes.dart b/pkg/compiler/lib/src/tree_ir/tree_ir_nodes.dart
index bb11b24b05f4f3f7e8aed225bc2e42ed789af796..02b6c8c41c5b578f70f255517c5bca0634df6c3a 100644
--- a/pkg/compiler/lib/src/tree_ir/tree_ir_nodes.dart
+++ b/pkg/compiler/lib/src/tree_ir/tree_ir_nodes.dart
@@ -542,8 +542,8 @@ abstract class StatementVisitor<S> {
   S visitExpressionStatement(ExpressionStatement node);
 }
 
-abstract class Visitor<S,E> implements ExpressionVisitor<E>,
-                                       StatementVisitor<S> {
+abstract class Visitor<S, E> implements ExpressionVisitor<E>,
+                                        StatementVisitor<S> {
    E visitExpression(Expression e) => e.accept(this);
    S visitStatement(Statement s) => s.accept(this);
 }