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}
diff --git a/sdk/android/api/org/webrtc/VideoCapturer.java b/sdk/android/api/org/webrtc/VideoCapturer.java
index 99a0729..8292fbd 100644
--- a/sdk/android/api/org/webrtc/VideoCapturer.java
+++ b/sdk/android/api/org/webrtc/VideoCapturer.java
@@ -16,6 +16,7 @@
 // Base interface for all VideoCapturers to implement.
 public interface VideoCapturer {
   // Interface used for providing callbacks to an observer.
+  @Deprecated
   public interface CapturerObserver {
     // Notify if the camera have been started successfully or not.
     // Called on a Java thread owned by VideoCapturer.
@@ -26,6 +27,13 @@
     void onFrameCaptured(VideoFrame frame);
   }
 
+  /** Deprecated, implementations should be update to implement the version below. */
+  @Deprecated
+  default void initialize(SurfaceTextureHelper surfaceTextureHelper, Context applicationContext,
+      CapturerObserver capturerObserver) {
+    throw new UnsupportedOperationException("Not implemented.");
+  }
+
   /**
    * This function is used to initialize the camera thread, the android application context, and the
    * capture observer. It will be called only once and before any startCapture() request. The
@@ -37,8 +45,12 @@
    * called. This also means that the caller can reuse the SurfaceTextureHelper to initialize a new
    * VideoCapturer once the previous VideoCapturer has been disposed.
    */
-  void initialize(SurfaceTextureHelper surfaceTextureHelper, Context applicationContext,
-      CapturerObserver capturerObserver);
+  // Our version of clang format doesn't understand default and messes up.
+  // clang-format off
+  default void initialize(SurfaceTextureHelper surfaceTextureHelper, Context applicationContext,
+      org.webrtc.CapturerObserver capturerObserver) {
+    initialize(surfaceTextureHelper, applicationContext, (CapturerObserver) capturerObserver);
+  }
 
   /**
    * Start capturing frames in a format that is as close as possible to {@code width x height} and