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

pkg/compiler/lib/src/cps_ir/cps_ir_builder_task.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library dart2js.ir_builder_task;
 
 import '../closure.dart' as closurelib;
 import '../closure.dart' hide ClosureScope;
+import '../common.dart';
 import '../common/names.dart' show
     Names,
     Selectors;
 import '../common/tasks.dart' show
     CompilerTask;
 import '../compiler.dart' show
     Compiler;
 import '../constants/expressions.dart';
 import '../dart_types.dart';
-import '../diagnostics/diagnostic_listener.dart' show
-    DiagnosticReporter;
-import '../diagnostics/invariant.dart' show
-    invariant;
 import '../elements/elements.dart';
 import '../elements/modelx.dart' show
     SynthesizedConstructorElementX,
     ConstructorBodyElementX,
     FunctionSignatureX;
 import '../io/source_information.dart';
 import '../js_backend/js_backend.dart' show
     JavaScriptBackend,
     SyntheticConstantKind;
 import '../resolution/tree_elements.dart' show
@@ skipping 3547 matching lines @@
     if (compiler.backend.isForeign(function)) {
       return handleForeignCode(node, function, argumentList, callStructure);
     } else {
       return irBuilder.buildStaticFunctionInvocation(function, callStructure,
           translateStaticArguments(argumentList, function, callStructure),
           sourceInformation:
               sourceInformationBuilder.buildCall(node, node.selector));
     }
   }
 }