remove dependency on compiler from resolution

tests/compiler/dart2js/mock_compiler.dart

 // Copyright (c) 2016, 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 mock_compiler;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:compiler/compiler.dart' as api;
@@ skipping 210 matching lines @@
 
   CollectingTreeElements resolveStatement(String text) {
     parsedTree = parseStatement(text);
     return resolveNodeStatement(parsedTree, new MockElement(mainApp));
   }
 
   TreeElementMapping resolveNodeStatement(Node tree,
                                           ExecutableElement element) {
     ResolverVisitor visitor =
         new ResolverVisitor(
-            this,
+            this.resolution,
             element,
-            new ResolutionRegistry(this,
+            new ResolutionRegistry(this.backend,
                 new CollectingTreeElements(element)),
             scope: new MockTypeVariablesScope(
                 element.enclosingElement.buildScope()));
     if (visitor.scope is LibraryScope ||
         visitor.scope is MockTypeVariablesScope) {
       visitor.scope = new MethodScope(visitor.scope, element);
     }
     visitor.visit(tree);
     visitor.scope = new LibraryScope(element.library);
     return visitor.registry.mapping;
   }
 
   resolverVisitor() {
     Element mockElement = new MockElement(mainApp.entryCompilationUnit);
     ResolverVisitor visitor =
         new ResolverVisitor(
-            this,
+            this.resolution,
             mockElement,
             new ResolutionRegistry(
-                this, new CollectingTreeElements(mockElement)),
+                this.backend, new CollectingTreeElements(mockElement)),
             scope: mockElement.enclosingElement.buildScope());
     visitor.scope = new MethodScope(visitor.scope, mockElement);
     return visitor;
   }
 
   parseScript(String text, [LibraryElement library]) {
     if (library == null) library = mainApp;
     parseUnit(text, this, library, registerSource);
   }
 
@@ skipping 140 matching lines @@
       trustTypeAnnotations: trustTypeAnnotations,
       enableTypeAssertions: enableTypeAssertions,
       enableUserAssertions: enableUserAssertions,
       expectedErrors: expectedErrors,
       expectedWarnings: expectedWarnings,
       outputProvider: outputProvider);
   compiler.registerSource(uri, code);
   compiler.diagnosticHandler = createHandler(compiler, code);
   return compiler;
 }