Support 'dart.library.X' env variables in the VM.

tests/language/language.status

Index: tests/language/language.status
diff --git a/tests/language/language.status b/tests/language/language.status
index ccdebbb742c7e1a055ed971df9c4f0647e40a352..e2a44ad8990387447ad32978a1d08bd7c37e507b 100644
--- a/tests/language/language.status
+++ b/tests/language/language.status
@@ -37,8 +37,6 @@ async_star_regression_2238_test: CompileTimeError, RuntimeError # drt only runti
 async_star_cancel_while_paused_test: RuntimeError
 async_star_await_pauses_test: Skip # Times out. Issue 23996
 
-library_env_test: RuntimeError
-
 [ ($compiler == none || $compiler == precompiler) && ($runtime == vm || $runtime == dart_precompiled) ]
 
 class_keyword_test/02: MissingCompileTimeError # Issue 13627
@@ -152,3 +150,15 @@ ct_const2_test: Pass, Crash # Incompatible flag --compile_all
 hello_dart_test: Pass, Crash # Incompatible flag --compile_all
 
 implicit_closure_test: Pass, Crash # --use_slow_path
+
+[ $compiler == none && $browser ]
+# The following tests are supposed to fail.
+library_env_test/has_io_support: RuntimeError, OK
+library_env_test/has_no_html_support: RuntimeError, OK
+library_env_test/has_no_mirror_support: RuntimeError, OK
+
+[ $compiler == none && $browser != true ]
+# The following tests are supposed to fail.
+library_env_test/has_html_support: RuntimeError, OK
+library_env_test/has_no_io_support: RuntimeError, OK
+library_env_test/has_no_mirror_support: RuntimeError, OK