infer null from context, this avoids bottom being introduced

pkg/analyzer/test/src/task/dart_test.dart

 // Copyright (c) 2015, 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 analyzer.test.src.task.dart_test;
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/dart/ast/visitor.dart';
 import 'package:analyzer/dart/element/element.dart';
@@ skipping 5403 matching lines @@
 ''');
     computeResult(new LibrarySpecificUnit(source, source), RESOLVED_UNIT12);
     CompilationUnit unit = outputs[RESOLVED_UNIT12];
 
     InterfaceType intType = context.typeProvider.intType;
     InterfaceType stringType = context.typeProvider.stringType;
     DartType bottomType = context.typeProvider.bottomType;
     DartType dynamicType = context.typeProvider.dynamicType;
 
     assertVariableDeclarationTypes(
-        AstFinder.getTopLevelVariable(unit, "x"), dynamicType, bottomType);
+        AstFinder.getTopLevelVariable(unit, "x"), dynamicType, dynamicType);
     assertVariableDeclarationTypes(
         AstFinder.getTopLevelVariable(unit, "y"), intType, intType);
     assertVariableDeclarationTypes(
-        AstFinder.getFieldInClass(unit, "A", "x"), dynamicType, bottomType);
+        AstFinder.getFieldInClass(unit, "A", "x"), dynamicType, dynamicType);
     assertVariableDeclarationTypes(
         AstFinder.getFieldInClass(unit, "A", "y"), intType, intType);
     assertVariableDeclarationTypes(
-        AstFinder.getFieldInClass(unit, "A", "x2"), dynamicType, bottomType);
+        AstFinder.getFieldInClass(unit, "A", "x2"), dynamicType, dynamicType);
     assertVariableDeclarationTypes(
         AstFinder.getFieldInClass(unit, "A", "y2"), intType, intType);
 
     List<Statement> statements =
         AstFinder.getStatementsInTopLevelFunction(unit, "test");
 
     assertAssignmentStatementTypes(statements[0], dynamicType, stringType);
     assertAssignmentStatementTypes(statements[1], intType, stringType);
     assertAssignmentStatementTypes(statements[2], dynamicType, stringType);
     assertAssignmentStatementTypes(statements[3], intType, stringType);
@@ skipping 356 matching lines @@
   /**
    * Fill [errorListener] with [result] errors in the current [task].
    */
   void _fillErrorListener(ResultDescriptor<List<AnalysisError>> result) {
     List<AnalysisError> errors = task.outputs[result] as List<AnalysisError>;
     expect(errors, isNotNull, reason: result.name);
     errorListener = new GatheringErrorListener();
     errorListener.addAll(errors);
   }
 }