NativeIO: Improving some web platform tests without functional changes.

This CL fixes some minor issues with NativeIO's web platform tests.
- The concurrent_io tests obtain a more unified structure to reduce the
chance of missing an await.
- createFile() is removed from close_async as the exact same function is
provided by resources/support.js.

Bug: 1157915
Change-Id: I3e33cc8d93e08c31dddc4d844310c92eeba31a7c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2587058
Commit-Queue: Richard Stotz <rstz@chromium.org>
Commit-Queue: Victor Costan <pwnall@chromium.org>
Reviewed-by: Victor Costan <pwnall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#836214}

third_party/blink/web_tests/external/wpt/native-io/close_async.tentative.https.any.js

 // META: title=NativeIO API: close().
 // META: global=window,worker
+// META: script=resources/support.js
 
 'use strict';
 
-// Returns a handle to a newly created file that holds some data.
-//
-// The file will be closed and deleted when the test ends.
-async function createFile(testCase, fileName) {
-  const file = await nativeIO.open(fileName);
-  testCase.add_cleanup(async () => {
-    await file.close();
-    await nativeIO.delete(fileName);
-  });
-
-  const writeSharedArrayBuffer = new SharedArrayBuffer(4);
-  const writtenBytes = new Uint8Array(writeSharedArrayBuffer);
-  writtenBytes.set([64, 65, 66, 67]);
-  const writeCount = await file.write(writtenBytes, 0);
-  assert_equals(writeCount, 4);
-
-  return file;
-}
-
 promise_test(async testCase => {
   const file = await createFile(testCase, 'file_name');
   assert_equals(await file.close(), undefined);

third_party/blink/web_tests/external/wpt/native-io/concurrent_io/concurrent_io_flush_async.tentative.https.any.js

@@ -15,7 +15,7 @@ for (let op of kOperations) {
     const res = op.prepare();
 
     const flushPromise = file.flush();
-    op.assertRejection(testCase, file, res);
+    await op.assertRejection(testCase, file, res);
 
     await flushPromise;
 

third_party/blink/web_tests/external/wpt/native-io/concurrent_io/concurrent_io_setLength_async.tentative.https.any.js

@@ -14,7 +14,7 @@ for (let op of kOperations) {
     const res = op.prepare();
 
     const setLengthPromise = file.setLength(5);
-    op.assertRejection(testCase, file, res);
+    await op.assertRejection(testCase, file, res);
 
     await setLengthPromise;
 

third_party/blink/web_tests/external/wpt/native-io/concurrent_io/operation_helpers.js

@@ -11,7 +11,7 @@
 //              and assertUnchanged. May be empty.
 //   assertRejection: A promise_rejects_dom(...) statement that calls
 //                      operation B. Takes the object returned by prepare as
-//                      third parameter.
+//                      third parameter. Returns a promise.
 //   assertUnchanged: An assertion that rejecting the promise did not change
 //                      the buffers in unexpected ways. The assertion does not
 //                      check if the file itself was not changed. This will be
@@ -30,8 +30,8 @@ const kOperations = [];
       const readBytes = new Uint8Array(readSharedArrayBuffer);
       return readBytes;
     },
-    assertRejection: (testCase, file, readBytes) => {
-      return promise_rejects_dom(testCase, 'InvalidStateError',
+    assertRejection: async (testCase, file, readBytes) => {
+      await promise_rejects_dom(testCase, 'InvalidStateError',
                                  file.read(readBytes, 4));
     },
     assertUnchanged: (readBytes) => {
@@ -48,8 +48,8 @@ const kOperations = [];
       writtenBytes.set([96, 97, 98, 99]);
       return writtenBytes;
     },
-    assertRejection: (testCase, file, writtenBytes) => {
-      return promise_rejects_dom(testCase, 'InvalidStateError',
+    assertRejection: async (testCase, file, writtenBytes) => {
+      await promise_rejects_dom(testCase, 'InvalidStateError',
                                  file.write(writtenBytes, 4));
     },
     assertUnchanged: () => {},
@@ -59,8 +59,8 @@ const kOperations = [];
   const kOpGetLength = {
     name: 'getLength',
     prepare: () => {},
-    assertRejection: (testCase, file) => {
-      return promise_rejects_dom(testCase, 'InvalidStateError',
+    assertRejection: async (testCase, file) => {
+      await promise_rejects_dom(testCase, 'InvalidStateError',
                                  file.getLength());
     },
     assertUnchanged: () => {},
@@ -82,7 +82,7 @@ const kOperations = [];
     name: 'setLength',
     prepare: () => {},
     assertRejection: async (testCase, file, readBytes) => {
-      return promise_rejects_dom(testCase, 'InvalidStateError',
+      await promise_rejects_dom(testCase, 'InvalidStateError',
                                 file.setLength(2));
     },
     assertUnchanged: () => {},