dart2js: Remove isD8 and isJsShell functions.

tests/compiler/dart2js_native/dart2js_native.status

Index: tests/compiler/dart2js_native/dart2js_native.status
diff --git a/tests/compiler/dart2js_native/dart2js_native.status b/tests/compiler/dart2js_native/dart2js_native.status
index 9eef5ac8e20ee4516ac42cd16952edc49ef319d5..6b5f6ee43bcc9f8f1bdeb62c60f641cc9ccbb0ef 100644
--- a/tests/compiler/dart2js_native/dart2js_native.status
+++ b/tests/compiler/dart2js_native/dart2js_native.status
@@ -17,14 +17,7 @@ fake_thing_test: Fail # Issue 13010
 [ $compiler == dart2js && $minified ]
 optimization_hints_test: Fail, OK # Test relies on unminified names.
 
-[ $browser || $runtime == jsshell ]
-only_pass_on_d8_test: Fail, OK # This test should only pass on D8.
-
-[ $browser || $runtime == d8 ]
-only_pass_on_jsshell_test: Fail, OK # This test should only pass on jsshell.
-
 [ $compiler == dart2js && $runtime == d8 && $system == windows ]
-only_pass_on_d8_test: Skip # Issue 17458
 compute_this_script_test: Skip # Issue 17458
 
 [ $compiler == dart2js && $cps_ir ]
@@ -117,8 +110,6 @@ native_window2_frog_test: Crash # Instance of 'TypeOperator': unimplemented in C
 native_wrapping_function3_frog_test: Crash # Instance of 'TypeOperator': unimplemented in CodeGenerator
 native_wrapping_function_frog_test: Crash # Instance of 'TypeOperator': unimplemented in CodeGenerator
 oddly_named_fields_test: Crash # cannot compile methods that need interceptor calling convention.
-only_pass_on_d8_test: Crash # cannot compile methods that need interceptor calling convention.
-only_pass_on_jsshell_test: Crash # cannot compile methods that need interceptor calling convention.
 optimization_hints_test: Crash # (JS('','String("in main function")')): handleStaticFunctionInvoke: foreign: function(JS)
 rti_only_native_test: Crash # (main): handleStaticFunctionGet: function(main)
 runtimetype_test: Crash # (JS('A','#',makeA())): handleStaticFunctionInvoke: foreign: function(JS)