Add mojo-based support for media device-change notifications.

content/renderer/media/media_devices_event_dispatcher.h

Index: content/renderer/media/media_devices_event_dispatcher.h
diff --git a/content/renderer/media/media_devices_event_dispatcher.h b/content/renderer/media/media_devices_event_dispatcher.h
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+++ b/content/renderer/media/media_devices_event_dispatcher.h
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+// 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 CONTENT_RENDERER_MEDIA_MEDIA_DEVICES_EVENT_DISPATCHER_H_
+#define CONTENT_RENDERER_MEDIA_MEDIA_DEVICES_EVENT_DISPATCHER_H_
+
+#include <stdint.h>
+
+#include <utility>
+#include <vector>
+
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+#include "base/threading/thread_checker.h"
+#include "content/common/content_export.h"
+#include "content/common/media/media_devices.h"
+#include "content/common/media/media_devices.mojom.h"
+#include "content/public/renderer/render_frame_observer.h"
+#include "content/public/renderer/render_frame_observer_tracker.h"
+
+namespace url {
+class Origin;
+}
+
+namespace content {
+
+// This class implements the logic for managing media device-change
+// subscriptions on the renderer process. It manages the generation of
+// subscription IDs and  handles the interaction with the Mojo objects that
+// communicate with the  browser process. There is at most one instance of this
+// class per frame.
+class CONTENT_EXPORT MediaDevicesEventDispatcher
+    : public RenderFrameObserver,
+      public RenderFrameObserverTracker<MediaDevicesEventDispatcher>,
+      public base::SupportsWeakPtr<MediaDevicesEventDispatcher> {
+ public:
+  using SubscriptionId = uint32_t;
+  using SubscriptionIdList = std::vector<SubscriptionId>;
+  using DevicesChangedCallback =
+      base::Callback<void(MediaDeviceType, const MediaDeviceInfoArray&)>;
+
+  // Returns a weak pointer to the MediaDevicesEventDispatcher for the given
+  // |render_frame|.
+  static base::WeakPtr<MediaDevicesEventDispatcher> GetForRenderFrame(
+      RenderFrame* render_frame);
+
+  ~MediaDevicesEventDispatcher() override;
+
+  // Register a callback for device-change notifications for a given device
+  // type. Returns a subscription ID that can be used to cancel the
+  // subscription.
+  SubscriptionId SubscribeDeviceChangeNotifications(
+      MediaDeviceType type,
+      const url::Origin& security_origin,
+      const DevicesChangedCallback& callback);
+
+  // Cancels a subscription identified with |subscription_id| to device-change
+  // notifications for device type |type|. If no subscription identified with
+  // |subscription_id| exists for device type |type|, this function returns
+  // without side effects.
+  void UnsubscribeDeviceChangeNotifications(MediaDeviceType type,
+                                            SubscriptionId subscription_id);
+
+  // Register a callback for device-change notifications for any device type.
+  // Returns a list of subscription IDs that can be used to cancel the
+  // subscriptions.
+  SubscriptionIdList SubscribeDeviceChangeNotifications(
+      const url::Origin& security_origin,
+      const DevicesChangedCallback& callback);
+
+  // Cancels subscriptions identified by |subscription_ids| to device-change
+  // notifications for all device types. This is implemented by invoking the
+  // single-parameter version of UnsubscribeDeviceChangeNotifications() for all
+  // device types.
+  void UnsubscribeDeviceChangeNotifications(
+      const SubscriptionIdList& subscription_ids);
+
+  // Dispatches an event notification to all registered callbacks for device
+  // type |type|. Should be invoked only by an object that detects changes in
+  // the set of media devices.
+  void DispatchDevicesChangedEvent(MediaDeviceType type,
+                                   const MediaDeviceInfoArray& device_infos);
+
+  // RenderFrameObserver override.
+  void OnDestruct() override;
+
+  void SetMediaDevicesDispatcherForTesting(
+      ::mojom::MediaDevicesDispatcherHostPtr media_devices_dispatcher);
+
+ private:
+  explicit MediaDevicesEventDispatcher(RenderFrame* render_frame);
+
+  const ::mojom::MediaDevicesDispatcherHostPtr& GetMediaDevicesDispatcher();
+
+  SubscriptionId current_id_;
+
+  using Subscription = std::pair<SubscriptionId, DevicesChangedCallback>;
+  using SubscriptionList = std::vector<Subscription>;
+  SubscriptionList device_change_subscriptions_[NUM_MEDIA_DEVICE_TYPES];
+
+  ::mojom::MediaDevicesDispatcherHostPtr media_devices_dispatcher_;
+
+  base::ThreadChecker thread_checker_;
+
+  DISALLOW_COPY_AND_ASSIGN(MediaDevicesEventDispatcher);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_RENDERER_MEDIA_MEDIA_DEVICES_EVENT_DISPATCHER_H_