pkg/logging: use UnmodifiableMapView from dart:collection

pkg/logging/pubspec.yaml

Index: pkg/logging/pubspec.yaml
diff --git a/pkg/logging/pubspec.yaml b/pkg/logging/pubspec.yaml
index 199f6539448d71dc8dfa02b143b54236133ab5e1..678ceef68d58fda633bdeb010b4ff3a485cc525b 100644
--- a/pkg/logging/pubspec.yaml
+++ b/pkg/logging/pubspec.yaml
@@ -1,15 +1,12 @@
 name: logging
-version: 0.9.1+1
+version: 0.9.1+2
 author: Dart Team <misc@dartlang.org>
 description: >
   Provides APIs for debugging and error logging. This library introduces
   abstractions similar to those used in other languages, such as the Closure
   JS Logger and java.util.logging.Logger.
-homepage: http://www.dartlang.org
-documentation: http://api.dartlang.org/docs/pkg/logging
+homepage: https://pub.dartlang.org/packages/logging
 environment:
-  sdk: '>=1.0.0 <2.0.0'
-dependencies:
-  collection: '>=0.9.0 <0.10.0'
+  sdk: '>=1.5.0 <2.0.0'
 dev_dependencies:
-  unittest: '>=0.9.0 <0.10.0'
+  unittest: '>=0.9.0 <0.12.0'