Auto merge of #24490 - servo-wpt-sync:wpt_update_18-10-2019, r=servo-wpt-sync

Sync WPT with upstream (18-10-2019)

Automated downstream sync of changes from upstream as of 18-10-2019.
[no-wpt-sync]
r? @servo-wpt-sync

1 files changed, 32 insertions, 0 deletions

diff --git a/tests/wpt/web-platform-tests/webgpu/framework/util/async_mutex.js b/tests/wpt/web-platform-tests/webgpu/framework/util/async_mutex.js
new file mode 100644
index 00000000000..cb900605bcf
--- /dev/null
+++ b/tests/wpt/web-platform-tests/webgpu/framework/util/async_mutex.js
@@ -0,0 +1,32 @@
+/**
+* AUTO-GENERATED - DO NOT EDIT. Source: https://github.com/gpuweb/cts
+**/
+
+function _defineProperty(obj, key, value) { if (key in obj) { Object.defineProperty(obj, key, { value: value, enumerable: true, configurable: true, writable: true }); } else { obj[key] = value; } return obj; }
+
+export class AsyncMutex {
+  constructor() {
+    _defineProperty(this, "newestQueueItem", void 0);
+  }
+
+  // Run an async function with a lock on this mutex.
+  // Waits until the mutex is available, locks it, runs the function, then releases it.
+  async with(fn) {
+    const p = (async () => {
+      // If the mutex is locked, wait for the last thing in the queue before running.
+      // (Everything in the queue runs in order, so this is after everything currently enqueued.)
+      if (this.newestQueueItem) {
+        await this.newestQueueItem;
+      }
+
+      return fn();
+    })(); // Push the newly-created Promise onto the queue by replacing the old "newest" item.
+
+
+    this.newestQueueItem = p; // And return so the caller can wait on the result.
+
+    return p;
+  }
+
+}
+//# sourceMappingURL=async_mutex.js.map
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