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

sdk/lib/io/common.dart

Index: sdk/lib/io/common.dart
diff --git a/sdk/lib/io/common.dart b/sdk/lib/io/common.dart
index 6258bcf9090372ec7f3b8b97dc5456bf464ede74..ea355801147789b965aafbea16516674ce4680f8 100644
--- a/sdk/lib/io/common.dart
+++ b/sdk/lib/io/common.dart
@@ -90,7 +90,7 @@ class OSError {
 
 // Object for holding a buffer and an offset.
 class _BufferAndStart {
-  List<int> buffer;
+  List buffer;
   int start;
   _BufferAndStart(this.buffer, this.start);
 }
@@ -100,7 +100,7 @@ class _BufferAndStart {
 // All other lists are first copied into a Uint8List. This has the added
 // benefit that it is faster to access from the C code as well.
 _BufferAndStart _ensureFastAndSerializableByteData(
-    List<int> buffer, int start, int end) {
+    List buffer, int start, int end) {
   if (buffer is Uint8List || buffer is Int8List) {
     return new _BufferAndStart(buffer, start);
   }