Revert "Add data-URI support class to dart:core (next to Uri)."

sdk/lib/core/core.dart

Index: sdk/lib/core/core.dart
diff --git a/sdk/lib/core/core.dart b/sdk/lib/core/core.dart
index 32f9fa0bed34b11b0441aac8ad1a636c32a2ddc3..a33c8fa30b1f1c6a5c58c029276218cc788724aa 100644
--- a/sdk/lib/core/core.dart
+++ b/sdk/lib/core/core.dart
@@ -155,12 +155,9 @@ library dart.core;
 import "dart:collection";
 import "dart:_internal" hide Symbol;
 import "dart:_internal" as internal show Symbol;
-import "dart:convert" show
-  Encoding, ASCII, LATIN1, UTF8,
-  BASE64, StringConversionSink, ChunkedConversionSink;
+import "dart:convert" show UTF8, LATIN1, Encoding;
 import "dart:math" show Random;  // Used by List.shuffle.
 import "dart:async" show Stream, Future;  // Used by Resource.
-import "dart:typed_data" show Uint8List;
 
 part "annotations.dart";
 part "bool.dart";