Revert "Use backend targets to run Kernel transformations in Fasta"

pkg/front_end/lib/src/fasta/kernel/kernel_target.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 fasta.kernel_target;
 
 import 'dart:async' show Future;
 
 import 'dart:io' show File;
 
@@ skipping 637 matching lines @@
           initializer.parent = constructor;
           constructor.initializers.insert(0, initializer);
         }
       }
     });
   }
 
   /// Run all transformations that are needed when building a program for the
   /// first time.
   void runBuildTransformations() {
-    backendTarget.performModularTransformationsOnLibraries(
-        loader.coreTypes, loader.hierarchy, loader.libraries,
-        logger: (String msg) => ticker.logMs(msg));
-    backendTarget.performGlobalTransformations(loader.coreTypes, program,
-        logger: (String msg) => ticker.logMs(msg));
+    transformMixinApplications();
+    otherTransformations();
+  }
+
+  void transformMixinApplications() {
+    mix.transformLibraries(
+        backendTarget, loader.coreTypes, loader.hierarchy, loader.libraries);
+    ticker.logMs("Transformed mixin applications");
+  }
+
+  void otherTransformations() {
+    if (!strongMode) {
+      // TODO(ahe): Don't generate type variables in the first place.
+      program.accept(new Erasure());
+      ticker.logMs("Erased type variables in generic methods");
+    }
+    if (errors.isEmpty && loader.collectCompileTimeErrors().isEmpty) {
+      // TODO(kmillikin): Make this run on a per-method basis.
+      transformAsync.transformLibraries(loader.coreTypes, loader.libraries);
+    }
+    ticker.logMs("Transformed async methods");
   }
 
   void verify() {
     var verifyErrors = verifyProgram(program);
     errors.addAll(verifyErrors.map((error) => '$error'));
     ticker.logMs("Verified program");
   }
 
   /// Tree-shakes most code from the [dillTarget] by visiting all other
   /// libraries in [program] and marking the APIs from the [dillTarget]
@@ skipping 33 matching lines @@
   }
   for (Constructor constructor in superclass.constructors) {
     if (constructor.name.name.isEmpty) {
       return constructor.function.requiredParameterCount == 0
           ? constructor
           : null;
     }
   }
   return null;
 }