Revert "Throw when adding something to a closed sink and improve documentation."

tests/standalone/io/http_content_length_test.dart

Index: tests/standalone/io/http_content_length_test.dart
diff --git a/tests/standalone/io/http_content_length_test.dart b/tests/standalone/io/http_content_length_test.dart
index 96dff03dae63ddfc7d85c223d980a7b255f0771b..f65f4052623de76a9bd10d2d1fab40d47d7b9918 100644
--- a/tests/standalone/io/http_content_length_test.dart
+++ b/tests/standalone/io/http_content_length_test.dart
@@ -37,9 +37,7 @@ void testNoBody(int totalConnections, bool explicitContentLength) {
       // After an explicit close, write becomes a state error
       // because we have said we will not add more.
       response.close();
-      Expect.throws(() {
-        response.write("x");
-      }, (e) => e is StateError);
+      response.write("x");
     }, onError: (e, trace) {
       String msg = "Unexpected server error $e";
       if (trace != null) msg += "\nStackTrace: $trace";
@@ -91,9 +89,7 @@ void testBody(int totalConnections, bool useHeader) {
           }
         });
         response.close();
-        Expect.throws(() {
-          response.write("x");
-        }, (e) => e is StateError);
+        response.write("x");
       });
     }, onError: (e, trace) {
       String msg = "Unexpected error $e";
@@ -153,9 +149,7 @@ void testBodyChunked(int totalConnections, bool useHeader) {
         response.write("x");
         response.write("x");
         response.close();
-        Expect.throws(() {
-          response.write("x");
-        }, (e) => e is StateError);
+        response.write("x");
       });
     }, onError: (e, trace) {
       String msg = "Unexpected error $e";