Import latest WritableStream tests from upstream

third_party/WebKit/LayoutTests/http/tests/streams/writable-streams/general.js

Index: third_party/WebKit/LayoutTests/http/tests/streams/writable-streams/general.js
diff --git a/third_party/WebKit/LayoutTests/http/tests/streams/writable-streams/general.js b/third_party/WebKit/LayoutTests/http/tests/streams/writable-streams/general.js
index 52741b83e0737c6b3f5473922002eddce0fe3c97..bcba6bfc81cdbbcc28000844640f7bc3c24415dd 100644
--- a/third_party/WebKit/LayoutTests/http/tests/streams/writable-streams/general.js
+++ b/third_party/WebKit/LayoutTests/http/tests/streams/writable-streams/general.js
@@ -152,4 +152,15 @@ promise_test(() => {
       .then(thisValue => assert_equals(thisValue, theSink, 'abort should be called as a method'));
 }, 'WritableStream should call underlying sink methods as methods');
 
+promise_test(() => {
+  const ws = new WritableStream();
+  const writer1 = ws.getWriter();
+  assert_equals(undefined, writer1.releaseLock(), 'releaseLock() should return undefined');
+  const writer2 = ws.getWriter();
+  assert_equals(undefined, writer1.releaseLock(), 'no-op releaseLock() should return undefined');
+  // Calling releaseLock() on writer1 should not interfere with writer2. If it did, then the ready promise would be
+  // rejected.
+  return writer2.ready;
+}, 'redundant releaseLock() is no-op');
+
 done();