Deprecate PeerConnectionFactory#createVideoSource(VideoCapturer).

This is done in preparation of moving VideoCapturer out of
video_api_java. Clients should update to using
createVideoSource(boolean).

CapturerObserver is moved to a separate file because it needs to stay
in video_api_java to allow VideoSource to depend on it.

Bug: webrtc:9496
Change-Id: I3c93f6bc4df553919dcbe05b00ef4c68f2c9ab60
Reviewed-on: https://webrtc-review.googlesource.com/87305
Reviewed-by: Magnus Jedvert <magjed@webrtc.org>
Commit-Queue: Sami Kalliomäki <sakal@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23868}

sdk/android/api/org/webrtc/CapturerObserver.java

@@ -0,0 +1,29 @@
+/*
+ *  Copyright 2018 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+package org.webrtc;
+
+/**
+ * Interface for observering a capturer. Passed to {@link VideoCapturer#initialize}. Provided by
+ * {@link VideoSource#getCapturerObserver}.
+ *
+ * All callbacks must be executed on a single thread.
+ *
+ * @note This will replace the deprecated VideoCapturer.CapturerObserver interface.
+ */
+public interface CapturerObserver extends VideoCapturer.CapturerObserver {
+  /** Notify if the capturer have been started successfully or not. */
+  @Override void onCapturerStarted(boolean success);
+  /** Notify that the capturer has been stopped. */
+  @Override void onCapturerStopped();
+
+  /** Delivers a captured frame. */
+  @Override void onFrameCaptured(VideoFrame frame);
+}