Worklet: Introduce "pending tasks struct" concept defined in the Worklet spec

third_party/WebKit/Source/core/workers/WorkletPendingTasks.cpp

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "core/workers/WorkletPendingTasks.h"
+
+#include "core/dom/DOMException.h"
+#include "core/dom/ExceptionCode.h"
+#include "platform/wtf/WTF.h"
+
+namespace blink {
+
+WorkletPendingTasks::WorkletPendingTasks(int counter,
+                                         ScriptPromiseResolver* resolver)
+    : counter_(counter), resolver_(resolver) {
+  DCHECK(IsMainThread());
+}
+
+void WorkletPendingTasks::Abort() {
+  DCHECK(IsMainThread());
+  // Step 3: "If script is null, then queue a task on outsideSettings's
+  // responsible event loop to run these steps:"
+  //   1: "If pendingTaskStruct's counter is not -1, then run these steps:"
+  //     1: "Set pendingTaskStruct's counter to -1."
+  //     2: "Reject promise with an "AbortError" DOMException."
+  if (counter_ != -1) {
+    counter_ = -1;
+    // TODO(nhiroki): This should be kAbortError.
+    resolver_->Reject(DOMException::Create(kNetworkError));
+  }
+}
+
+void WorkletPendingTasks::DecrementCounter() {
+  DCHECK(IsMainThread());
+  // Step 5: "Queue a task on outsideSettings's responsible event loop to run
+  // these steps:"
+  //   1: "If pendingTaskStruct's counter is not -1, then run these steps:"
+  //     1: "Decrement pendingTaskStruct's counter by 1."
+  //     2: "If pendingTaskStruct's counter is 0, then resolve promise."
+  if (counter_ != -1) {
+    --counter_;
+    if (counter_ == 0)
+      resolver_->Resolve();
+  }
+}
+
+}  // namespace blink