Consume Mojo services directly in Blink's WebUSB implementation.

third_party/WebKit/Source/bindings/core/v8/MojoPromiseAdapter.h

+// Copyright 2016 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 MojoPromiseAdapter_h
+#define MojoPromiseAdapter_h
+
+#include "bindings/core/v8/ScriptPromiseResolver.h"
+
+namespace blink {
+
+class ExecutionContext;
+
+// This class wraps a ScriptPromiseResolver.
+//
+// When the callback() method is called ownership of this object is passed to
+// a new mojo::Callback. Subclasses must implement a Run() method matching the
+// callback type and override the destructor to either resolve or reject with
+// an appropriate value to handle closure of the Mojo pipe.
+template <typename Callback>
+class MojoPromiseAdapter : public Callback::Runnable {
+    WTF_MAKE_NONCOPYABLE(MojoPromiseAdapter);
+
+public:
+    MojoPromiseAdapter(ScriptPromiseResolver* resolver) : m_resolver(resolver)
+    {
+    }
+
+    ~MojoPromiseAdapter() override
+    {
+        // Before this object is destroyed a subclass must call resolve() or
+        // reject() unless the execution context is inactive.
+        ASSERT(!active());
+    }
+
+    void resolve()
+    {
+        ASSERT(active());
+        m_resolver->resolve();
+        m_resolver = nullptr;
+    }
+
+    template <typename T>
+    void resolve(T value)
+    {
+        ASSERT(active());
+        m_resolver->resolve(value);
+        m_resolver = nullptr;
+    }
+
+    void reject()
+    {
+        ASSERT(active());
+        m_resolver->reject();
+        m_resolver = nullptr;
+    }
+
+    template <typename T>
+    void reject(T value)
+    {
+        ASSERT(active());
+        m_resolver->reject(value);
+        m_resolver = nullptr;
+    }
+
+    bool active() const
+    {
+        return m_resolver && executionContext() && !executionContext()->activeDOMObjectsAreStopped();
+    }
+
+    Callback callback()
+    {
+#if ENABLE(ASSERT)
+        // This method passes ownership of |this| to the callback it returns so
+        // it may only be called once.
+        ASSERT(!m_isCallbackCalled);
+        m_isCallbackCalled = true;
+#endif
+        return Callback(this);
+    }
+
+    ExecutionContext* executionContext() const { return m_resolver->getExecutionContext(); }
+
+private:
+    Persistent<ScriptPromiseResolver> m_resolver;
+#if ENABLE(ASSERT)
+    bool m_isCallbackCalled = false;
+#endif
+};
+
+}
+
+#endif // MojoPromiseAdapter_h