dart2dart: Implementation of simple try/catch.

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

Index: pkg/compiler/lib/src/tree_ir/tree_ir_tracer.dart
diff --git a/pkg/compiler/lib/src/tree_ir/tree_ir_tracer.dart b/pkg/compiler/lib/src/tree_ir/tree_ir_tracer.dart
index 9828c9418bee7ff62f2844e9d13b354ef7555767..475bdaebcc83e98153b1237970018f9718d2ccbe 100644
--- a/pkg/compiler/lib/src/tree_ir/tree_ir_tracer.dart
+++ b/pkg/compiler/lib/src/tree_ir/tree_ir_tracer.dart
@@ -141,6 +141,11 @@ class BlockCollector extends StatementVisitor {
     ifTargets[node.next] = nextBlock;
   }
 
+  visitTry(Try node) {
+    // It's not obvious how we want to represent try statements here.
+    // TODO(kmillikin).
+  }
+
   visitExpressionStatement(ExpressionStatement node) {
     _addStatement(node);
     visitStatement(node.next);
@@ -275,6 +280,11 @@ class TreeTracer extends TracerUtil with StatementVisitor, PassMixin {
     printStatement(null, "then $nextTarget" );
   }
 
+  visitTry(Try node) {
+    // It's not obvious how we want to represent try statements here.
+    // TODO(kmillikin).
+  }
+
   visitExpressionStatement(ExpressionStatement node) {
     printStatement(null, expr(node.expression));
   }