Remove dart:platform library.

tests/lib/lib.status

Index: tests/lib/lib.status
diff --git a/tests/lib/lib.status b/tests/lib/lib.status
index 6004f4abc6ac0f145ab3415bcd63c02dd6723725..032341d402625d6c61546bb9db53fc484197c50c 100644
--- a/tests/lib/lib.status
+++ b/tests/lib/lib.status
@@ -130,10 +130,6 @@ async/timer_not_available_test: Fail, OK # only meant to test when there is no w
 mirrors/*: Skip # http://dartbug.com/11511
 async/schedule_microtask6_test: Fail             # Issue 10957 - may be related to issue 10910
 async/schedule_microtask3_test: RuntimeError # Issue 13719: Please triage this failure.
-platform/package_root_test: Fail # Issue 14451
-platform/script_test: Fail # Issue 14451
-platform/isolate_test: Fail # Issue 14451
-
 
 [ $compiler == dart2dart && $minified ]
 json/json_test: Fail                            # Issue 10961
@@ -190,7 +186,6 @@ mirrors/immutable_collections_test: Fail # Issue 11857, Issue 14321
 mirrors/library_uri_io_test: Skip # Not intended for drt as it uses dart:io.
 mirrors/local_isolate_test: Skip # http://dartbug.com/12188
 async/schedule_microtask6_test: Fail # Issue 10910
-platform/isolate_test: Skip # Issue 14444
 
 [ $compiler == none && $runtime == drt && $mode == debug ]
 mirrors/hierarchy_invariants_test: Pass, Slow # Issue 14449
@@ -215,9 +210,6 @@ async/timer_cancel2_test: Pass, Timeout # Issue 13719: Please triage this failur
 # Issue 13921: spawnFunction is not allowed on Dartium's DOM thread.
 async/timer_isolate_test: Fail
 
-[ $compiler == none && ($runtime == drt || $runtime == dartium) && $system == windows ]
-platform/uri_test: Fail # Issue 14504
-
 [ ($compiler != none && $runtime != none) || ($compiler == none && ($runtime != dartium && $runtime != drt)) ]
 async/schedule_microtask_test: Fail # Issue 9001, Issue 9002