Release the camera when WebRTC is not visible in Android

content/browser/renderer_host/media/video_capture_manager.h

 // Copyright (c) 2012 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.
 
 // VideoCaptureManager is used to open/close, start/stop, enumerate available
 // video capture devices, and manage VideoCaptureController's.
 // All functions are expected to be called from Browser::IO thread. Some helper
 // functions (*OnDeviceThread) will dispatch operations to the device thread.
 // VideoCaptureManager will open OS dependent instances of VideoCaptureDevice.
 // A device can only be opened once.
@@ skipping 66 matching lines @@
 
   // Called by VideoCaptureHost to remove |client_handler|. If this is the last
   // client of the device, the |controller| and its VideoCaptureDevice may be
   // destroyed. The client must not access |controller| after calling this
   // function.
   void StopCaptureForClient(VideoCaptureController* controller,
                             VideoCaptureControllerID client_id,
                             VideoCaptureControllerEventHandler* client_handler,
                             bool aborted_due_to_error);
 
+  // Called by VideoCaptureHost to pause to update video buffer specified by
+  // |client_id| and |client_handler|. If all clients of |controller| are
+  // paused, the corresponding device will be closed.
+  void PauseCaptureForClient(
+      VideoCaptureController* controller,
+      VideoCaptureControllerID client_id,
+      VideoCaptureControllerEventHandler* client_handler);
+
+  // Called by VideoCaptureHost to resume to update video buffer specified by
+  // |client_id| and |client_handler|. The |session_id| and |params| should be
+  // same as those used in StartCaptureForClient().
+  // If this is first active client of |controller|, device will be allocated
+  // and it will take a little time to resume.
+  // Allocating device could failed if other app holds the camera, the error
+  // will be notified through VideoCaptureControllerEventHandler::OnError().
+  void ResumeCaptureForClient(
+      media::VideoCaptureSessionId session_id,
+      const media::VideoCaptureParams& params,
+      VideoCaptureController* controller,
+      VideoCaptureControllerID client_id,
+      VideoCaptureControllerEventHandler* client_handler);
+
   // Retrieves all capture supported formats for a particular device. Returns
   // false if the |capture_session_id| is not found. The supported formats are
   // cached during device(s) enumeration, and depending on the underlying
   // implementation, could be an empty list.
   bool GetDeviceSupportedFormats(
       media::VideoCaptureSessionId capture_session_id,
       media::VideoCaptureFormats* supported_formats);
 
   // Retrieves the format(s) currently in use.  Returns false if the
   // |capture_session_id| is not found. Returns true and |formats_in_use|
@@ skipping 146 matching lines @@
   // Accessed on the device thread only.
   std::map<media::VideoCaptureSessionId, gfx::NativeViewId>
       notification_window_ids_;
 
   DISALLOW_COPY_AND_ASSIGN(VideoCaptureManager);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_MEDIA_VIDEO_CAPTURE_MANAGER_H_