Update mojo sdk to rev c02a28868825edfa57ab77947b8cb15e741c5598

third_party/mojo/src/mojo/public/dart/BUILD.gn

Index: third_party/mojo/src/mojo/public/dart/BUILD.gn
diff --git a/third_party/mojo/src/mojo/public/dart/BUILD.gn b/third_party/mojo/src/mojo/public/dart/BUILD.gn
index b820d96a702fc436c57832871b93d3abf25cebe3..fb145558ef8551c43cdb07f9c90d5a83f1ca9926 100644
--- a/third_party/mojo/src/mojo/public/dart/BUILD.gn
+++ b/third_party/mojo/src/mojo/public/dart/BUILD.gn
@@ -21,10 +21,6 @@ dart_mojo_sdk_sources = [
   "lib/src/stub.dart",
   "lib/src/union.dart",
   "lib/src/types.dart",
-  "sdk_ext/internal.dart",
-  "sdk_ext/src/handle_watcher.dart",
-  "sdk_ext/src/natives.dart",
-  "sdk_ext/src/timer_queue.dart",
 ]
 
 dartzip_package("dart") {
@@ -49,6 +45,9 @@ dart_pkg("mojo") {
               "README.md",
             ]
 
+  sdk_ext_directory = "sdk_ext"
+  sdk_ext_mappings = [ "dart:mojo.internal,internal.dart" ]
+
   # List of mojom targets that the mojo pkg exports
   deps = [
     "../interfaces",