Remove runtime 'dart_app' as it became identical to 'vm'.

tests/isolate/isolate.status

Index: tests/isolate/isolate.status
diff --git a/tests/isolate/isolate.status b/tests/isolate/isolate.status
index 8274317473d0e14157c04f87c0bf467ee9f854ad..e767897ddedd3a6c8452aa015868dfd355721833 100644
--- a/tests/isolate/isolate.status
+++ b/tests/isolate/isolate.status
@@ -2,17 +2,17 @@
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
-[ ($runtime == vm || $runtime == dart_precompiled || $runtime == dart_app) ]
+[ $runtime == vm || $runtime == dart_precompiled ]
 browser/*: SkipByDesign  # Browser specific tests
 isolate_stress_test: Skip # Issue 12588: Uses dart:html. This should be able to pass when we have wrapper-less tests.
 
-[ $runtime != vm || $mode == product ]
+[ $runtime != vm || $mode == product || $compiler == app_jit ]
 checked_test: Skip # Unsupported.
 
-[ ($runtime == vm || $runtime == dart_precompiled || $runtime == dart_app) && $arch == mips && $mode == debug ]
+[ ($runtime == vm || $runtime == dart_precompiled) && $arch == mips && $mode == debug ]
 mandel_isolate_test: Skip # Uses 600 MB Ram on our 1 GB test device.
 
-[ ($compiler == none || $compiler == precompiler || $compiler == dart2app || $compiler == dart2appjit) ]
+[ $compiler == none || $compiler == precompiler || $compiler == app_jit ]
 compile_time_error_test/01: Skip # Issue 12587
 ping_test: Skip           # Resolve test issues
 ping_pause_test: Skip     # Resolve test issues
@@ -191,7 +191,7 @@ stacktrace_message_test: SkipByDesign
 static_function_test: SkipByDesign
 unresolved_ports_test: SkipByDesign
 
-[ $runtime == dart_precompiled || $runtime == dart_app ]
+[ $runtime == dart_precompiled || $compiler == app_jit ]
 count_test: Skip # Isolate.spawnUri
 cross_isolate_message_test: Skip # Isolate.spawnUri
 deferred_in_isolate2_test: Skip # Isolate.spawnUri