Remove TODOs from KernelConditionalExpression._inferExpression.

pkg/front_end/lib/src/fasta/kernel/kernel_shadow_ast.dart

 // Copyright (c) 2017, 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.
 
 /// This file declares a "shadow hierarchy" of concrete classes which extend
 /// the kernel class hierarchy, adding methods and fields needed by the
 /// BodyBuilder.
 ///
 /// Instances of these classes may be created using the factory methods in
 /// `ast_factory.dart`.
@@ skipping 261 matching lines @@
   @override
   DartType _inferExpression(
       KernelTypeInferrer inferrer, DartType typeContext, bool typeNeeded) {
     typeNeeded =
         inferrer.listener.conditionalExpressionEnter(this, typeContext) ||
             typeNeeded;
     if (!inferrer.isTopLevel) {
       inferrer.inferExpression(
           condition, inferrer.coreTypes.boolClass.rawType, false);
     }
-    // TODO(paulberry): is it correct to pass the context down?
     DartType thenType = inferrer.inferExpression(then, typeContext, true);
     DartType otherwiseType =
         inferrer.inferExpression(otherwise, typeContext, true);
-    // TODO(paulberry): the spec proposal says we should only use LUB if the
-    // typeContext is `null`.  If typeContext is non-null, we should use the
-    // greatest closure of the context with respect to `?`
     DartType type = inferrer.typeSchemaEnvironment
         .getLeastUpperBound(thenType, otherwiseType);
     staticType = type;
     var inferredType = typeNeeded ? type : null;
     inferrer.listener.conditionalExpressionExit(this, inferredType);
     return inferredType;
   }
 }
 
 /// Shadow object for [ConstructorInvocation].
@@ skipping 1600 matching lines @@
   }
 
   visitChildren(v) {
     return internalError("Internal error: Unsupported operation.");
   }
 
   transformChildren(v) {
     return internalError("Internal error: Unsupported operation.");
   }
 }