Rename apiimpl.Compiler to CompilerImpl.

tests/compiler/dart2js/mirrors_used_test.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.
 
 /// Test that the @MirrorsUsed annotation suppress hints and that only
 /// requested elements are retained for reflection.
 library dart2js.test.mirrors_used_test;
 
 import 'package:expect/expect.dart';
 import "package:async_helper/async_helper.dart";
 
 import 'memory_compiler.dart' show
     runCompiler;
 
 import 'package:compiler/src/apiimpl.dart' show
-    Compiler;
+    CompilerImpl;
 
 import 'package:compiler/src/constants/values.dart' show
     ConstantValue,
     TypeConstantValue;
 
 import 'package:compiler/src/elements/elements.dart' show
     Element,
     Elements;
 
 import 'package:compiler/src/js_backend/js_backend.dart' show
@@ skipping 21 matching lines @@
 
   throw '$uri:$begin:$end: $kind: $message';
 }
 
 void main() {
   asyncTest(() async {
     var result = await runCompiler(
       memorySourceFiles: MEMORY_SOURCE_FILES,
       diagnosticHandler: new LegacyCompilerDiagnostics(expectOnlyVerboseInfo),
       options: ['--enable-experimental-mirrors']);
-    Compiler compiler = result.compiler;
+    CompilerImpl compiler = result.compiler;
     print('');
     List generatedCode =
         Elements.sortedByPosition(compiler.enqueuer.codegen.generatedCode.keys);
     for (var element in generatedCode) {
       print(element);
     }
     print('');
 
     // This assertion can fail for two reasons:
     // 1. Too many elements retained for reflection.
@@ skipping 112 matching lines @@
 library lib;
 
 import 'dart:mirrors';
 
 useReflect(type) {
   print(new Symbol('Foo'));
   print(MirrorSystem.getName(reflectClass(type).owner.qualifiedName));
 }
 """,
 };