Make source information on conditions mandatory in CPS

pkg/compiler/lib/src/io/position_information.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.
 
 /// Source information system mapping that attempts a semantic mapping between
 /// offsets of JavaScript code points to offsets of Dart code points.
 
 library dart2js.source_information.position;
 
 import '../common.dart';
@@ skipping 286 matching lines @@
   SourceInformation buildBinary(Node node) => buildBegin(node);
 
   @override
   SourceInformation buildCatch(Node node) => buildBegin(node);
 
   @override
   SourceInformation buildIs(Node node) => buildBegin(node);
 
   @override
   SourceInformation buildAs(Node node) => buildBegin(node);
+
+  @override
+  SourceInformation buildSwitch(Node node) => buildBegin(node);
+
+  @override
+  SourceInformation buildSwitchCase(Node node) => buildBegin(node);
 }
 
 /// The start, end and closing offsets for a [js.Node].
 class CodePosition {
   final int startPosition;
   final int endPosition;
   final int closingPosition;
 
   CodePosition(this.startPosition, this.endPosition, this.closingPosition);
 
@@ skipping 1005 matching lines @@
 
   @override
   CodePosition operator [](js.Node node) {
     CodePosition codePosition = codePositions[node];
     if (codePosition == null) {
       coverage.registerNodesWithoutOffset(node);
    }
     return codePosition;
   }
 }