Remove Sink and move CollectionSink to async.

sdk/lib/_internal/compiler/compiler.dart

Index: sdk/lib/_internal/compiler/compiler.dart
diff --git a/sdk/lib/_internal/compiler/compiler.dart b/sdk/lib/_internal/compiler/compiler.dart
index cf7eb2acb14b523a2109aead124eb4a63e4df25b..bbee705a0386725a035cfbb0f97a335768543b70 100644
--- a/sdk/lib/_internal/compiler/compiler.dart
+++ b/sdk/lib/_internal/compiler/compiler.dart
@@ -22,7 +22,7 @@ typedef Future<String> CompilerInputProvider(Uri uri);
 typedef Future<String> ReadStringFromUri(Uri uri);
 
 /**
- * Returns a [Sink] that will serve as compiler output for the given
+ * Returns a [StreamSink] that will serve as compiler output for the given
  * component.
  *
  * Components are identified by [name] and [extension]. By convention,
@@ -41,7 +41,8 @@ typedef Future<String> ReadStringFromUri(Uri uri);
  * As more features are added to the compiler, new names and
  * extensions may be introduced.
  */
-typedef Sink<String> CompilerOutputProvider(String name, String extension);
+typedef StreamSink<String> CompilerOutputProvider(String name,
+                                                  String extension);
 
 /**
  * Invoked by the compiler to report diagnostics. If [uri] is