pkg/compiler: fix imports

pkg/compiler/lib/src/tracer.dart

Index: pkg/compiler/lib/src/tracer.dart
diff --git a/pkg/compiler/lib/src/tracer.dart b/pkg/compiler/lib/src/tracer.dart
index 359ea772340a0a8cefe17e3085b034d29cead348..09b8b98157e6d7094770b749343eb74a006db8d7 100644
--- a/pkg/compiler/lib/src/tracer.dart
+++ b/pkg/compiler/lib/src/tracer.dart
@@ -5,13 +5,14 @@
 library tracer;
 
 import 'dart:async' show EventSink;
+
 import '../compiler.dart' as api;
 import 'common/work.dart' show ItemCompilationContext;
 import 'compiler.dart' show Compiler;
-import 'ssa/nodes.dart' as ssa show HGraph;
-import 'ssa/ssa_tracer.dart' show HTracer;
 import 'cps_ir/cps_ir_nodes.dart' as cps_ir;
 import 'cps_ir/cps_ir_tracer.dart' show IRTracer;
+import 'ssa/nodes.dart' as ssa show HGraph;
+import 'ssa/ssa_tracer.dart' show HTracer;
 import 'tree_ir/tree_ir_nodes.dart' as tree_ir;
 import 'tree_ir/tree_ir_tracer.dart' show TreeTracer;
 import 'util/util.dart' show Indentation;