Revert "Fix remaining strong-mode warnings and errors in dart:io."

sdk/lib/io/platform_impl.dart

Index: sdk/lib/io/platform_impl.dart
diff --git a/sdk/lib/io/platform_impl.dart b/sdk/lib/io/platform_impl.dart
index 75278443388f638eed4f792de401ef8c68604cbf..4ce43ea1e65507f09bbfac97a6919a66a90297ca 100644
--- a/sdk/lib/io/platform_impl.dart
+++ b/sdk/lib/io/platform_impl.dart
@@ -39,7 +39,7 @@ class _Platform {
 
   // Cache the OS environemnt. This can be an OSError instance if
   // retrieving the environment failed.
-  static var/*OSError|Map<String,String>*/ _environmentCache;
+  static var _environmentCache;
 
   static int get numberOfProcessors => _numberOfProcessors();
   static String get pathSeparator => _pathSeparator();
@@ -62,9 +62,7 @@ class _Platform {
       var env = _environment();
       if (env is !OSError) {
         var isWindows = operatingSystem == 'windows';
-        var result = isWindows
-            ? new _CaseInsensitiveStringMap<String>()
-            : new Map<String, String>();
+        var result = isWindows ? new _CaseInsensitiveStringMap() : new Map();
         for (var str in env) {
           // The Strings returned by [_environment()] are expected to be
           // valid environment entries, but exceptions have been seen
@@ -86,7 +84,7 @@ class _Platform {
     if (_environmentCache is OSError) {
       throw _environmentCache;
     } else {
-      return _environmentCache as Object/*=Map<String, String>*/;
+      return _environmentCache;
     }
   }
 
@@ -108,7 +106,7 @@ class _CaseInsensitiveStringMap<V> implements Map<String, V> {
   V putIfAbsent(String key, V ifAbsent()) {
     return _map.putIfAbsent(key.toUpperCase(), ifAbsent);
   }
-  void addAll(Map<String, V> other) {
+  void addAll(Map other) {
     other.forEach((key, value) => this[key.toUpperCase()] = value);
   }
   V remove(Object key) => key is String ? _map.remove(key.toUpperCase()) : null;