Simplify use of ContentDecryptionModuleResult with promises

Source/modules/encryptedmedia/ContentDecryptionModuleResultPromise.h

+// Copyright 2014 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.
+
+#ifndef ContentDecryptionModuleResultPromise_h
+#define ContentDecryptionModuleResultPromise_h
+
+#include "bindings/core/v8/ScriptPromiseResolver.h"
+#include "core/dom/ExceptionCode.h"
+#include "platform/ContentDecryptionModuleResult.h"
+
+namespace blink {
+
+ExceptionCode WebCdmExceptionToExceptionCode(WebContentDecryptionModuleException);
+
+// This class wraps the promise resolver to simplify creation of
+// ContentDecryptionModuleResult objects. The default implementations of the
+// complete(), completeWithSession(), etc. methods will reject the promise
+// with an error. It needs to be subclassed and the appropriate complete()
+// method overridden to resolve the promise as needed.
+class ContentDecryptionModuleResultPromise : public ContentDecryptionModuleResult {
+public:
+    virtual ~ContentDecryptionModuleResultPromise();
+
+    // ContentDecryptionModuleResult implementation.
+    virtual void complete() override;
+    virtual void completeWithSession(WebContentDecryptionModuleResult::SessionStatus) override;
+    virtual void completeWithError(WebContentDecryptionModuleException, unsigned long systemCode, const WebString&) final;
+
+    // It is only valid to call this before completion.
+    ScriptPromise promise();
+
+    virtual void trace(Visitor*);
+
+protected:
+    explicit ContentDecryptionModuleResultPromise(ScriptState*);
+
+    // Resolves the promise with |value|. Used by subclasses to resolve the
+    // promise.
+    template <typename... T>
+    void resolve(T... value)
+    {
+        m_resolver->resolve(value...);
+        m_resolver.clear();
+    }
+
+    // Rejects the promise with a DOMException.
+    void reject(ExceptionCode, const String& errorMessage);
+
+    ExecutionContext* executionContext() const;
+
+private:
+    RefPtr<ScriptPromiseResolver> m_resolver;
+};
+
+} // namespace blink
+
+#endif // ContentDecryptionModuleResultPromise_h