Rename apiimpl.Compiler to CompilerImpl.

tests/compiler/dart2js/deferred_load_mapping_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.
 
 import 'package:expect/expect.dart';
 import "package:async_helper/async_helper.dart";
 import 'memory_source_file_helper.dart';
 import "memory_compiler.dart";
 
 void main() {
   asyncTest(() async {
     var collector = new OutputCollector();
     CompilationResult result = await runCompiler(
         memorySourceFiles: MEMORY_SOURCE_FILES,
         options: ['--deferred-map=deferred_map.json'],
         outputProvider: collector);
-    Compiler compiler = result.compiler;
+    CompilerImpl compiler = result.compiler;
     // Ensure a mapping file is output.
     Expect.isNotNull(
         collector.getOutput("deferred_map.json", "deferred_map"));
 
     Map mapping = compiler.deferredLoadTask.computeDeferredMap();
     // Test structure of mapping.
     Expect.equals("<unnamed>", mapping["main.dart"]["name"]);
     Expect.equals(2, mapping["main.dart"]["imports"]["lib1"].length);
     Expect.equals(2, mapping["main.dart"]["imports"]["lib2"].length);
     Expect.equals(1, mapping["main.dart"]["imports"]["convert"].length);
@@ skipping 65 matching lines @@
 
 bar1() {
   return "hello";
 }
 
 bar2() {
   return 2;
 }
 """,
 };