Add option to suppress type-check whitelisting

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 a9bd363bc87e2b951724acb0d47db25701fda687..3f935d69c861a1e090687c3948d6673ffe43d5e8 100644
--- a/pkg/dev_compiler/tool/sdk_expected_errors.txt
+++ b/pkg/dev_compiler/tool/sdk_expected_errors.txt
@@ -51,8 +51,6 @@
 [error] Invalid override. The type of 'JsArray.[]=' ('(Object, E) → void') isn't a subtype of 'JsObject.[]=' ('(Object, dynamic) → dynamic'). (dart:js, line 363, col 3)
 [error] The return type 'double' isn't a 'T', as defined by the method 'min'. (dart:math, line 90, col 16)
 [error] The return type 'double' isn't a 'T', as defined by the method 'max'. (dart:math, line 125, col 16)
-[warning] Unsafe implicit cast from 'List<dynamic>' to 'List<String>'. This usually indicates that type information was lost and resulted in 'dynamic' and/or a place that will have a failure at runtime. (dart:_js_helper/regexp_helper.dart, line 140, col 43)
-[warning] Unsafe implicit cast from 'List<dynamic>' to 'List<String>'. This usually indicates that type information was lost and resulted in 'dynamic' and/or a place that will have a failure at runtime. (dart:_js_helper/regexp_helper.dart, line 152, col 43)
 [warning] Unsafe implicit cast from 'Function' to '(dynamic) → FutureOr<T>'. This usually indicates that type information was lost and resulted in 'dynamic' and/or a place that will have a failure at runtime. (dart:async/future_impl.dart, line 151, col 11)
 [warning] Unsafe implicit cast from '(T) → dynamic' to '(T) → FutureOr<E>'. This usually indicates that type information was lost and resulted in 'dynamic' and/or a place that will have a failure at runtime. (dart:async/future_impl.dart, line 249, col 57)
 [warning] Unsafe implicit cast from 'StreamSubscription<dynamic>' to 'StreamSubscription<T>'. This usually indicates that type information was lost and resulted in 'dynamic' and/or a place that will have a failure at runtime. (dart:async/stream_impl.dart, line 1011, col 42)