Make EventStreamSubscription DDC safe.

pkg/dev_compiler/tool/sdk_expected_errors.txt

Index: pkg/dev_compiler/tool/sdk_expected_errors.txt
diff --git a/pkg/dev_compiler/tool/sdk_expected_errors.txt b/pkg/dev_compiler/tool/sdk_expected_errors.txt
index dde8a4e115b5b3e0514f7b0621d5a6b901fac44b..0a3d26eaad4c12c0bd77fffaa8562da7b5c7986a 100644
--- a/pkg/dev_compiler/tool/sdk_expected_errors.txt
+++ b/pkg/dev_compiler/tool/sdk_expected_errors.txt
@@ -16,7 +16,6 @@
 [error] Const constructors can't throw exceptions. (dart:core/int.dart, line 34, col 5)
 [error] Only redirecting factory constructors can be declared to be 'const'. (dart:core/string.dart, line 156, col 9)
 [error] Const constructors can't throw exceptions. (dart:core/string.dart, line 157, col 5)
-[error] Invalid override. The type of '_EventStreamSubscription.asFuture' ('([dynamic]) → Future<dynamic>') isn't a subtype of 'StreamSubscription<T>.asFuture' ('<E>([E]) → Future<E>'). (dart:html, line 40152, col 3)
 [error] Couldn't infer type parameter 'S'; 'RandomAccessFile' must be of type 'File'. (dart:io/file_impl.dart, line 216, col 19)
 [error] The argument type '([dynamic]) → void' can't be assigned to the parameter type '(_ConnectionInfo) → dynamic'. (dart:io/http_impl.dart, line 1633, col 19)
 [error] The return type 'StreamSubscription<int>' isn't a 'StreamSubscription<List<int>>', as defined by the method 'listen'. (dart:io/http_parser.dart, line 208, col 14)
@@ -78,8 +77,7 @@
 [warning] The final variables 'form', 'labels' and '5' more must be initialized. (dart:html, line 32069, col 3)
 [warning] The final variables 'readyState' and 'track' must be initialized. (dart:html, line 33056, col 3)
 [warning] The final variables 'decodedFrameCount', 'droppedFrameCount' and '2' more must be initialized. (dart:html, line 33754, col 3)
-[warning] Unsafe implicit cast from '(T) → void' to '(Event) → dynamic'. This usually indicates that type information was lost and resulted in 'dynamic' and/or a place that will have a failure at runtime. (dart:html, line 40090, col 67)
-[warning] Unsafe implicit cast from '(T) → void' to '(Event) → dynamic'. This usually indicates that type information was lost and resulted in 'dynamic' and/or a place that will have a failure at runtime. (dart:html, line 40112, col 45)
+[warning] Unsafe implicit cast from '(T) → void' to '(Event) → dynamic'. This usually indicates that type information was lost and resulted in 'dynamic' and/or a place that will have a failure at runtime. (dart:html, line 40126, col 45)
 [warning] Unsafe implicit cast from 'List<dynamic>' to 'List<int>'. This usually indicates that type information was lost and resulted in 'dynamic' and/or a place that will have a failure at runtime. (dart:io/data_transformer.dart, line 492, col 23)
 [warning] Unsafe implicit cast from 'Stream<dynamic>' to 'Stream<FileSystemEntity>'. This usually indicates that type information was lost and resulted in 'dynamic' and/or a place that will have a failure at runtime. (dart:io/directory_impl.dart, line 239, col 12)
 [warning] Unsafe implicit cast from 'Future<dynamic>' to 'Future<List<int>>'. This usually indicates that type information was lost and resulted in 'dynamic' and/or a place that will have a failure at runtime. (dart:io/file_impl.dart, line 484, col 14)