ImageCapture: ScopedResultCallback

media/capture/video/scoped_callback.h

Index: media/capture/video/scoped_callback.h
diff --git a/media/capture/video/scoped_callback.h b/media/capture/video/scoped_callback.h
new file mode 100644
index 0000000000000000000000000000000000000000..dd1b33460927f3ae45cea211fbebe7f5ae57dd26
--- /dev/null
+++ b/media/capture/video/scoped_callback.h
@@ -0,0 +1,52 @@
+// 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_CALLBACK_H_
+#define MEDIA_CAPTURE_VIDEO_SCOPED_CALLBACK_H_
+
+#include "base/callback_forward.h"
+
+namespace media {
+
+// This class wraps a |callback_| and guarantees that it will be called on
+// destruction and according to the provided OnErrorCallback if it hasn't been
+// retrieved before (via PassCallback()). Inspired by ScopedWebCallbacks
+// template.
+template <typename CallbackType>
+class ScopedCallback {
+  MOVE_ONLY_TYPE_FOR_CPP_03(ScopedCallback);
+
+ public:
+  using OnErrorCallback = base::Callback<void(const CallbackType&)>;
+  ScopedCallback(const CallbackType& callback,
+                 const OnErrorCallback& on_error_callback)
+      : callback_(std::move(callback)), on_error_callback_(on_error_callback) {}

[Reilly Grant (use Gerrit), 2016/05/26 00:27:45]

nit: The move here and below are unnecessary.

[mcasas, 2016/05/26 17:24:04]

Done.

+
+  ~ScopedCallback() {
+    if (!callback_.is_null())
+      on_error_callback_.Run(callback_);
+  }
+
+  ScopedCallback(ScopedCallback&& other) { *this = std::move(other); }
+
+  ScopedCallback& operator=(ScopedCallback&& other) {
+    callback_ = other.PassCallback();
+    on_error_callback_ = other.on_error_callback_;
+    return *this;
+  }
+
+  CallbackType PassCallback() {
+    CallbackType callback = callback_;
+    callback_.reset();
+    return std::move(callback);
+  }
+
+ private:
+  CallbackType callback_;
+  OnErrorCallback on_error_callback_;
+};
+
+}  // namespace media
+
+#endif  // MEDIA_CAPTURE_VIDEO_SCOPED_CALLBACK_H_