Start work on a non-complete type inferrer. Currently only analyzes return types.

tests/compiler/dart2js/cpa_inference_test.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.
 
 import "dart:uri";
 import "../../../sdk/lib/_internal/compiler/implementation/elements/elements.dart";
 import '../../../sdk/lib/_internal/compiler/implementation/scanner/scannerlib.dart';
 import '../../../sdk/lib/_internal/compiler/implementation/source_file.dart';
 import '../../../sdk/lib/_internal/compiler/implementation/types/types.dart';
 import '../../../sdk/lib/_internal/compiler/implementation/tree/tree.dart';
@@ skipping 35 matching lines @@
   BaseType int;
   BaseType double;
   BaseType num;
   BaseType bool;
   BaseType string;
   BaseType list;
   BaseType map;
   BaseType nullType;
 
   AnalysisResult(MockCompiler compiler) : this.compiler = compiler {
-    inferrer = compiler.typesTask.concreteTypesInferrer;
+    inferrer = compiler.typesTask.typesInferrer;
     int = inferrer.baseTypes.intBaseType;
     double = inferrer.baseTypes.doubleBaseType;
     num = inferrer.baseTypes.numBaseType;
     bool = inferrer.baseTypes.boolBaseType;
     string = inferrer.baseTypes.stringBaseType;
     list = inferrer.baseTypes.listBaseType;
     map = inferrer.baseTypes.mapBaseType;
     nullType = new NullBaseType();
     Element mainElement = compiler.mainApp.find(buildSourceString('main'));
     ast = mainElement.parseNode(compiler);
@@ skipping 103 matching lines @@
   class Dynamic_ {}
   bool identical(Object a, Object b) {}''';
 
 AnalysisResult analyze(String code, {int maxConcreteTypeSize: 1000}) {
   Uri uri = new Uri.fromComponents(scheme: 'source');
   MockCompiler compiler = new MockCompiler(
       coreSource: CORELIB,
       enableConcreteTypeInference: true,
       maxConcreteTypeSize: maxConcreteTypeSize);
   compiler.sourceFiles[uri.toString()] = new SourceFile(uri.toString(), code);
-  compiler.typesTask.concreteTypesInferrer.testMode = true;
+  compiler.typesTask.typesInferrer.testMode = true;
   compiler.runCompiler(uri);
   return new AnalysisResult(compiler);
 }
 
 testDynamicBackDoor() {
   final String source = r"""
     main () {
       var x = "__dynamic_for_test";
       x;
     }
@@ skipping 878 matching lines @@
   // testFieldInitialization(); // TODO(polux)
   testSendWithWrongArity();
   testBigTypesWidening1();
   testBigTypesWidening2();
   testDynamicIsAbsorbing();
   testLists();
   testListWithCapacity();
   testEmptyList();
   testIsCheck();
 }