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 a820ef01f4fabc1aacf83e646dfadc7315f19c14..a0fc4d25a8efa34d793be421301eead9a6e1b427 100644
--- a/tests/language/language.status
+++ b/tests/language/language.status
@@ -45,8 +45,6 @@ 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
-
 accessor_conflict_export2_test: RuntimeError # Issue 25625
 accessor_conflict_import2_test: RuntimeError # Issue 25625
 accessor_conflict_import_prefixed2_test: RuntimeError # Issue 25625
@@ -197,3 +195,15 @@ regress_22443_test: Skip
 
 [ $runtime == vm && $mode == product ]
 vm/type_vm_test: Fail,OK  # Expects exact type name.
+
+[ $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