Revert "Move dart2js from sdk/lib/_internal/compiler to pkg/compiler"

tests/compiler/dart2js/compiler_alt.dart

Index: tests/compiler/dart2js/compiler_alt.dart
diff --git a/tests/compiler/dart2js/compiler_alt.dart b/tests/compiler/dart2js/compiler_alt.dart
index 5296de0802bfa42e8c72cb983282b3bf0731ae71..030e584ae350b67dd2d366de831f707f25cc7336 100644
--- a/tests/compiler/dart2js/compiler_alt.dart
+++ b/tests/compiler/dart2js/compiler_alt.dart
@@ -6,14 +6,14 @@
 /// for later inspection.
 ///
 /// Use this in testing to inspect the compiler after compilation by setting
-/// the `compileFunc` variable in `package:compiler/src/dart2js.dart`
+/// the `compileFunc` variable in `package:compiler/implementation/dart2js.dart`
 /// to [compiler] before calling the `internalMain` function.
 
 library dart2js.alt;
 
 import 'dart:async';
 import 'package:compiler/compiler.dart';
-import 'package:compiler/src/apiimpl.dart';
+import 'package:compiler/implementation/apiimpl.dart';
 
 Compiler compiler;