Use common.dart to re-export commonly used entities.

pkg/compiler/lib/src/js_backend/codegen/task.dart

Index: pkg/compiler/lib/src/js_backend/codegen/task.dart
diff --git a/pkg/compiler/lib/src/js_backend/codegen/task.dart b/pkg/compiler/lib/src/js_backend/codegen/task.dart
index 0e12e63214d426e21afa405dde03acd1b732293b..a9d529263169ea94c622a92efca55fea5b846b2a 100644
--- a/pkg/compiler/lib/src/js_backend/codegen/task.dart
+++ b/pkg/compiler/lib/src/js_backend/codegen/task.dart
@@ -10,38 +10,42 @@ import 'codegen.dart';
 import 'unsugar.dart';
 
 import '../js_backend.dart';
+
+import '../../common.dart';
 import '../../common/codegen.dart' show
     CodegenWorkItem;
 import '../../common/tasks.dart' show
-    CompilerTask;
+    CompilerTask,
+    GenericTask;
 import '../../compiler.dart' show
     Compiler;
 import '../../constants/constant_system.dart';
+import '../../cps_ir/cps_ir_builder_task.dart';
 import '../../cps_ir/cps_ir_nodes.dart' as cps;
+import '../../cps_ir/cps_ir_nodes_sexpr.dart';
 import '../../cps_ir/cps_ir_integrity.dart';
-import '../../cps_ir/cps_ir_builder_task.dart';
-import '../../diagnostics/diagnostic_listener.dart' show
-    DiagnosticReporter;
+import '../../cps_ir/optimizers.dart';
+import '../../cps_ir/optimizers.dart' as cps_opt;
+import '../../cps_ir/type_mask_system.dart';
 import '../../diagnostics/invariant.dart' show
     DEBUG_MODE;
-import '../../tree_ir/tree_ir_nodes.dart' as tree_ir;
-import '../../types/types.dart' show TypeMask, UnionTypeMask, FlatTypeMask,
-    ForwardingTypeMask;
 import '../../elements/elements.dart';
 import '../../js/js.dart' as js;
-import '../../io/source_information.dart' show SourceInformationStrategy;
+import '../../js_backend/codegen/codegen.dart';
+import '../../io/source_information.dart' show
+    SourceInformationStrategy;
 import '../../tree_ir/tree_ir_builder.dart' as tree_builder;
-import '../../cps_ir/optimizers.dart';
-import '../../cps_ir/optimizers.dart' as cps_opt;
 import '../../tracer.dart';
-import '../../js_backend/codegen/codegen.dart';
 import '../../ssa/ssa.dart' as ssa;
 import '../../tree_ir/optimization/optimization.dart';
 import '../../tree_ir/optimization/optimization.dart' as tree_opt;
 import '../../tree_ir/tree_ir_integrity.dart';
-import '../../cps_ir/cps_ir_nodes_sexpr.dart';
-import '../../cps_ir/type_mask_system.dart';
-import '../../common/tasks.dart';
+import '../../tree_ir/tree_ir_nodes.dart' as tree_ir;
+import '../../types/types.dart' show
+    FlatTypeMask,
+    ForwardingTypeMask,
+    TypeMask,
+    UnionTypeMask;
 
 class CpsFunctionCompiler implements FunctionCompiler {
   final ConstantSystem constantSystem;