getUserMeida: report device starting states

media/capture/video/video_capture_device.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.
 //
 // VideoCaptureDevice is the abstract base class for realizing video capture
 // device support in Chromium. It provides the interface for OS dependent
 // implementations.
 // The class is created and functions are invoked on a thread owned by
 // VideoCaptureManager. Capturing is done on other threads, depending on the OS
 // specific implementation.
@@ skipping 57 matching lines @@
   static constexpr double kNoUtilizationRecorded = -1.0;
 };
 
 class CAPTURE_EXPORT VideoCaptureDevice
     : public VideoFrameConsumerFeedbackObserver {
  public:
 
   // Interface defining the methods that clients of VideoCapture must have. It
   // is actually two-in-one: clients may implement OnIncomingCapturedData() or
   // ReserveOutputBuffer() + OnIncomingCapturedVideoFrame(), or all of them.
-  // All clients must implement OnError().
+  // All methods may be called as soon as AllocateAndStart() of the
+  // corresponding VideoCaptureDevice is invoked. The methods for buffer
+  // reservation and frame delivery may be called from arbitrary threads but
+  // are guaranteed to be called non-concurrently. The status reporting methods
+  // (OnStarted, OnLog, OnError) may be called concurrently.
   class CAPTURE_EXPORT Client {
    public:
     // Struct bundling several parameters being passed between a
     // VideoCaptureDevice and its VideoCaptureDevice::Client.
     struct CAPTURE_EXPORT Buffer {
      public:
       // Destructor-only interface for encapsulating scoped access permission to
       // a Buffer.
       class CAPTURE_EXPORT ScopedAccessPermission {
        public:
@@ skipping 104 matching lines @@
     // be StopAndDeAllocate()-ed. |reason| is a text description of the error.
     virtual void OnError(const tracked_objects::Location& from_here,
                          const std::string& reason) = 0;
 
     // VideoCaptureDevice requests the |message| to be logged.
     virtual void OnLog(const std::string& message) {}
 
     // Returns the current buffer pool utilization, in the range 0.0 (no buffers
     // are in use by producers or consumers) to 1.0 (all buffers are in use).
     virtual double GetBufferPoolUtilization() const = 0;
+
+    // VideoCaptureDevice reports it's successfully started.
+    virtual void OnStarted() = 0;
   };
 
   ~VideoCaptureDevice() override;
 
   // Prepares the video capturer for use. StopAndDeAllocate() must be called
   // before the object is deleted.
   virtual void AllocateAndStart(const VideoCaptureParams& params,
                                 std::unique_ptr<Client> client) = 0;
 
   // In cases where the video capturer self-pauses (e.g., a screen capturer
@@ skipping 75 matching lines @@
 
  private:
   // Gets the power line frequency from the current system time zone if this is
   // defined, otherwise returns 0.
   PowerLineFrequency GetPowerLineFrequencyForLocation() const;
 };
 
 }  // namespace media
 
 #endif  // MEDIA_CAPTURE_VIDEO_VIDEO_CAPTURE_DEVICE_H_