Delete dart_backend from compiler.

tests/compiler/dart2js/backend_dart/opt_cyclic_redundant_phi_test.dart

-// Copyright (c) 2014, 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 'opt_redundant_phi_test.dart';
-
-// The 'cyclic deps' IR tests removal of redundant phis with cyclic
-// dependencies.
-//
-//  void main() {
-//    var x = 0;
-//    var y = x;
-//    for (int i = 0; i < 10; i++) {
-//      if (i == -1) x = y;
-//      if (i == -1) y = x;
-//    }
-//    print(x);
-//    print(y);
-//  }
-
-String CYCLIC_DEPS_IN = """
-(FunctionDefinition main (return) (LetPrim v0 (Constant 0))
-  (LetPrim v1 (Constant 0))
-  (LetCont* (k0 v2 v3 v4)
-    (LetCont (k1)
-      (LetCont (k2 v5)
-        (LetCont (k3 v6) (LetPrim v7 (Constant null))
-          (InvokeContinuation return v7))
-        (InvokeStatic print v3 k3))
-      (InvokeStatic print v2 k2))
-    (LetCont (k4) (LetPrim v8 (Constant 1))
-      (LetCont (k5 v9)
-        (LetCont (k6 v10)
-          (LetCont (k7 v11) (LetPrim v12 (Constant 1))
-            (LetCont (k8 v13)
-              (LetCont (k9 v14)
-                (LetCont (k10 v15)
-                  (LetPrim v16 (Constant 1))
-                  (LetCont (k11 v17)
-                    (InvokeContinuation* k0 v11 v15 v17))
-                  (InvokeMethod v4 + v16 k11))
-                (LetCont (k12) (InvokeContinuation k10 v11))
-                (LetCont (k13) (InvokeContinuation k10 v3))
-                (Branch (IsTrue v14) k12 k13))
-              (InvokeMethod v4 == v13 k9))
-            (InvokeMethod v12 unary- k8))
-          (LetCont (k14) (InvokeContinuation k7 v3))
-          (LetCont (k15) (InvokeContinuation k7 v2))
-          (Branch (IsTrue v10) k14 k15))
-        (InvokeMethod v4 == v9 k6))
-      (InvokeMethod v8 unary- k5))
-    (LetPrim v18 (Constant 10))
-    (LetCont (k16 v19) (Branch (IsTrue v19) k4 k1))
-    (InvokeMethod v4 < v18 k16))
-  (InvokeContinuation k0 v0 v0 v1))
-""";
-
-String CYCLIC_DEPS_OUT = """
-(FunctionDefinition main (return) (LetPrim v0 (Constant 0))
-  (LetPrim v1 (Constant 0))
-  (LetCont* (k0 v2)
-    (LetCont (k1)
-      (LetCont (k2 v3)
-        (LetCont (k3 v4) (LetPrim v5 (Constant null))
-          (InvokeContinuation return v5))
-        (InvokeStatic print v0 k3))
-      (InvokeStatic print v0 k2))
-    (LetCont (k4) (LetPrim v6 (Constant 1))
-      (LetCont (k5 v7)
-        (LetCont (k6 v8)
-          (LetCont (k7) (LetPrim v9 (Constant 1))
-            (LetCont (k8 v10)
-              (LetCont (k9 v11)
-                (LetCont (k10)
-                  (LetPrim v12 (Constant 1))
-                  (LetCont (k11 v13)
-                    (InvokeContinuation* k0 v13))
-                  (InvokeMethod v2 + v12 k11))
-                (LetCont (k12) (InvokeContinuation k10))
-                (LetCont (k13) (InvokeContinuation k10))
-                (Branch (IsTrue v11) k12 k13))
-              (InvokeMethod v2 == v10 k9))
-            (InvokeMethod v9 unary- k8))
-          (LetCont (k14) (InvokeContinuation k7))
-          (LetCont (k15) (InvokeContinuation k7))
-          (Branch (IsTrue v8) k14 k15))
-        (InvokeMethod v2 == v7 k6))
-      (InvokeMethod v6 unary- k5))
-    (LetPrim v14 (Constant 10))
-    (LetCont (k16 v15) (Branch (IsTrue v15) k4 k1))
-    (InvokeMethod v2 < v14 k16))
-  (InvokeContinuation k0 v1))
-""";
-
-void main() {
-  testRedundantPhi(CYCLIC_DEPS_IN, CYCLIC_DEPS_OUT);
-}