ImageCapture: ScopedResultCallback

media/capture/video/scoped_result_callback.h

Index: media/capture/video/scoped_result_callback.h
diff --git a/media/capture/video/scoped_result_callback.h b/media/capture/video/scoped_result_callback.h
new file mode 100644
index 0000000000000000000000000000000000000000..9c937e8a2815b2ecbd883f3397d2a40344ff9e4d
--- /dev/null
+++ b/media/capture/video/scoped_result_callback.h
@@ -0,0 +1,58 @@
+// 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 MEDIA_CAPTURE_VIDEO_SCOPED_RESULT_CALLBACK_H_
+#define MEDIA_CAPTURE_VIDEO_SCOPED_RESULT_CALLBACK_H_
+
+#include "base/callback_forward.h"
+#include "mojo/public/cpp/bindings/callback.h"
+
+namespace media {
+
+// This class guarantees that |callback_| has either been called or will pass it
+// to |on_error_callback_| on destruction. Inspired by ScopedWebCallbacks<>.
+template <typename CallbackType>
+class ScopedResultCallback {
+  MOVE_ONLY_TYPE_FOR_CPP_03(ScopedResultCallback);
+
+ public:
+  using OnErrorCallback = base::Callback<void(const CallbackType&)>;
+  ScopedResultCallback(const CallbackType& callback,
+                       const OnErrorCallback& on_error_callback)
+      : callback_(callback), on_error_callback_(on_error_callback) {}
+
+  ~ScopedResultCallback() {
+    if (!callback_.is_null())
+      on_error_callback_.Run(callback_);
+  }
+
+  ScopedResultCallback(ScopedResultCallback&& other) {
+    *this = std::move(other);
+  }
+
+  ScopedResultCallback& operator=(ScopedResultCallback&& other) {
+    callback_ = other.callback_;
+    other.callback_.reset();
+    on_error_callback_ = other.on_error_callback_;
+    other.on_error_callback_.Reset();
+    return *this;
+  }
+
+  template <typename... Args>
+  void Run(Args... args) {
+    on_error_callback_.Reset();
+    // TODO(mcasas): Use base::ResetAndReturn() when mojo::Callback<> is
+    // compatible with base::Callback<>, see https://crbug.com/596521.
+    callback_.Run(std::forward<Args>(args)...);
+    callback_.reset();
+  }
+
+ private:
+  CallbackType callback_;
+  OnErrorCallback on_error_callback_;
+};
+
+}  // namespace media
+
+#endif  // MEDIA_CAPTURE_VIDEO_SCOPED_RESULT_CALLBACK_H_