Rename the global inference task and reduce it's API surface by introducing the

pkg/compiler/lib/src/ssa/ssa.dart

 // Copyright (c) 2012, 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 ssa;
 
 import '../common/codegen.dart' show CodegenWorkItem;
 import '../common/tasks.dart' show CompilerTask;
 import '../elements/elements.dart' show Element, FunctionElement;
 import '../io/source_information.dart';
 import '../js/js.dart' as js;
 import '../js_backend/backend.dart' show JavaScriptBackend, FunctionCompiler;
 
 import 'builder.dart';
 import 'builder_kernel.dart';
 import 'codegen.dart';
 import 'nodes.dart';
 import 'optimize.dart';
-import 'types.dart';
 
 class SsaFunctionCompiler implements FunctionCompiler {
   final SsaCodeGeneratorTask generator;
   final SsaBuilderTask builder;
   final SsaKernelBuilderTask builderKernel;
   final SsaOptimizerTask optimizer;
   final JavaScriptBackend backend;
   final bool useKernel;
 
   SsaFunctionCompiler(JavaScriptBackend backend,
@@ skipping 20 matching lines @@
   }
 
   Iterable<CompilerTask> get tasks {
     return <CompilerTask>[
       useKernel ? builderKernel : builder,
       optimizer,
       generator
     ];
   }
 }