Introduce class that handles native wrapping of AndroidVideoTrackSource

This CL attempts to do separation of concerns by introducing a simple
class that only handles JNI wrapping of a C++ AndroidVideoTrackSource.
This layer can be easiliy mocked out in Java unit tests.

Bug: webrtc:10247
Change-Id: Idbdbfde6d3e00b64f3f310f76505801fa496580d
Reviewed-on: https://webrtc-review.googlesource.com/c/121562
Commit-Queue: Magnus Jedvert <magjed@webrtc.org>
Reviewed-by: Sami Kalliomäki <sakal@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#26556}

sdk/android/src/java/org/webrtc/NativeAndroidVideoTrackSource.java

@@ -0,0 +1,64 @@
+/*
+ *  Copyright (c) 2019 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;
+
+import android.support.annotation.Nullable;
+import org.webrtc.VideoFrame;
+
+/**
+ * This class is meant to be a simple layer that only handles the JNI wrapping of a C++
+ * AndroidVideoTrackSource, that can easily be mocked out in Java unit tests. Refrain from adding
+ * any unnecessary logic to this class.
+ */
+class NativeAndroidVideoTrackSource {
+  // Pointer to webrtc::jni::AndroidVideoTrackSource.
+  private final long nativeAndroidVideoTrackSource;
+
+  public NativeAndroidVideoTrackSource(long nativeAndroidVideoTrackSource) {
+    this.nativeAndroidVideoTrackSource = nativeAndroidVideoTrackSource;
+  }
+
+  /**
+   * Set the state for the native MediaSourceInterface. Maps boolean to either
+   * SourceState::kLive or SourceState::kEnded.
+   */
+  public void setState(boolean isLive) {
+    nativeSetState(nativeAndroidVideoTrackSource, isLive);
+  }
+
+  /** Pass a frame to the native AndroidVideoTrackSource. */
+  public void onFrameCaptured(VideoFrame frame) {
+    nativeOnFrameCaptured(nativeAndroidVideoTrackSource, frame.getBuffer().getWidth(),
+        frame.getBuffer().getHeight(), frame.getRotation(), frame.getTimestampNs(),
+        frame.getBuffer());
+  }
+
+  /**
+   * Calling this function will cause frames to be scaled down to the requested resolution. Also,
+   * frames will be cropped to match the requested aspect ratio, and frames will be dropped to match
+   * the requested fps.
+   */
+  public void adaptOutputFormat(VideoSource.AspectRatio targetLandscapeAspectRatio,
+      @Nullable Integer maxLandscapePixelCount, VideoSource.AspectRatio targetPortraitAspectRatio,
+      @Nullable Integer maxPortraitPixelCount, @Nullable Integer maxFps) {
+    nativeAdaptOutputFormat(nativeAndroidVideoTrackSource, targetLandscapeAspectRatio.width,
+        targetLandscapeAspectRatio.height, maxLandscapePixelCount, targetPortraitAspectRatio.width,
+        targetPortraitAspectRatio.height, maxPortraitPixelCount, maxFps);
+  }
+
+  private static native void nativeSetState(long nativeAndroidVideoTrackSource, boolean isLive);
+  private static native void nativeAdaptOutputFormat(long nativeAndroidVideoTrackSource,
+      int landscapeWidth, int landscapeHeight, @Nullable Integer maxLandscapePixelCount,
+      int portraitWidth, int portraitHeight, @Nullable Integer maxPortraitPixelCount,
+      @Nullable Integer maxFps);
+  private static native void nativeOnFrameCaptured(long nativeAndroidVideoTrackSource, int width,
+      int height, int rotation, long timestampNs, VideoFrame.Buffer buffer);
+}