Make VideoFrame.Buffer implementations lock-free.

Replaces lock-based implementation with AtomicInteger.

Bug: webrtc:7749
Change-Id: I226093b0af2090c080dfd4f87ed8f33a3f9efbd8
Reviewed-on: https://webrtc-review.googlesource.com/64162
Commit-Queue: Sami Kalliomäki <sakal@webrtc.org>
Reviewed-by: Magnus Jedvert <magjed@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22798}

sdk/android/src/java/org/webrtc/NV12Buffer.java

@@ -11,6 +11,7 @@
 package org.webrtc;
 
 import java.nio.ByteBuffer;
+import javax.annotation.Nullable;
 
 @JNINamespace("webrtc::jni")
 public class NV12Buffer implements VideoFrame.Buffer {
@@ -19,21 +20,16 @@ public class NV12Buffer implements VideoFrame.Buffer {
   private final int stride;
   private final int sliceHeight;
   private final ByteBuffer buffer;
-  private final Runnable releaseCallback;
-  private final Object refCountLock = new Object();
-
-  private int refCount;
+  private final RefCountDelegate refCountDelegate;
 
   public NV12Buffer(int width, int height, int stride, int sliceHeight, ByteBuffer buffer,
-      Runnable releaseCallback) {
+      @Nullable Runnable releaseCallback) {
     this.width = width;
     this.height = height;
     this.stride = stride;
     this.sliceHeight = sliceHeight;
     this.buffer = buffer;
-    this.releaseCallback = releaseCallback;
-
-    refCount = 1;
+    this.refCountDelegate = new RefCountDelegate(releaseCallback);
   }
 
   @Override
@@ -53,18 +49,12 @@ public class NV12Buffer implements VideoFrame.Buffer {
 
   @Override
   public void retain() {
-    synchronized (refCountLock) {
-      ++refCount;
-    }
+    refCountDelegate.retain();
   }
 
   @Override
   public void release() {
-    synchronized (refCountLock) {
-      if (--refCount == 0 && releaseCallback != null) {
-        releaseCallback.run();
-      }
-    }
+    refCountDelegate.release();
   }
 
   @Override

sdk/android/src/java/org/webrtc/NV21Buffer.java

@@ -11,22 +11,21 @@
 package org.webrtc;
 
 import java.nio.ByteBuffer;
+import java.util.concurrent.atomic.AtomicInteger;
+import javax.annotation.Nullable;
 
 @JNINamespace("webrtc::jni")
 public class NV21Buffer implements VideoFrame.Buffer {
   private final byte[] data;
   private final int width;
   private final int height;
-  private final Runnable releaseCallback;
-  private final Object refCountLock = new Object();
+  private final RefCountDelegate refCountDelegate;
 
-  private int refCount = 1;
-
-  public NV21Buffer(byte[] data, int width, int height, Runnable releaseCallback) {
+  public NV21Buffer(byte[] data, int width, int height, @Nullable Runnable releaseCallback) {
     this.data = data;
     this.width = width;
     this.height = height;
-    this.releaseCallback = releaseCallback;
+    this.refCountDelegate = new RefCountDelegate(releaseCallback);
   }
 
   @Override
@@ -48,18 +47,12 @@ public class NV21Buffer implements VideoFrame.Buffer {
 
   @Override
   public void retain() {
-    synchronized (refCountLock) {
-      ++refCount;
-    }
+    refCountDelegate.retain();
   }
 
   @Override
   public void release() {
-    synchronized (refCountLock) {
-      if (--refCount == 0 && releaseCallback != null) {
-        releaseCallback.run();
-      }
-    }
+    refCountDelegate.release();
   }
 
   @Override

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

@@ -0,0 +1,41 @@
+/*
+ *  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;
+
+import java.util.concurrent.atomic.AtomicInteger;
+import javax.annotation.Nullable;
+
+/**
+ * Implementation of RefCounted that executes a Runnable once the ref count reaches zero.
+ */
+class RefCountDelegate implements RefCounted {
+  private final AtomicInteger refCount = new AtomicInteger(1);
+  private final @Nullable Runnable releaseCallback;
+
+  /**
+   * @param releaseCallback Callback that will be executed once the ref count reaches zero.
+   */
+  public RefCountDelegate(@Nullable Runnable releaseCallback) {
+    this.releaseCallback = releaseCallback;
+  }
+
+  @Override
+  public void retain() {
+    refCount.incrementAndGet();
+  }
+
+  @Override
+  public void release() {
+    if (refCount.decrementAndGet() == 0 && releaseCallback != null) {
+      releaseCallback.run();
+    }
+  }
+}

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

@@ -12,6 +12,8 @@ package org.webrtc;
 
 import android.graphics.Matrix;
 import java.nio.ByteBuffer;
+import java.util.concurrent.atomic.AtomicInteger;
+import javax.annotation.Nullable;
 
 /**
  * Android texture buffer backed by a SurfaceTextureHelper's texture. The buffer calls
@@ -24,20 +26,17 @@ class TextureBufferImpl implements VideoFrame.TextureBuffer {
   private final int id;
   private final Matrix transformMatrix;
   private final SurfaceTextureHelper surfaceTextureHelper;
-  private final Runnable releaseCallback;
-  private final Object refCountLock = new Object();
-  private int refCount;
+  private final RefCountDelegate refCountDelegate;
 
   public TextureBufferImpl(int width, int height, Type type, int id, Matrix transformMatrix,
-      SurfaceTextureHelper surfaceTextureHelper, Runnable releaseCallback) {
+      SurfaceTextureHelper surfaceTextureHelper, @Nullable Runnable releaseCallback) {
     this.width = width;
     this.height = height;
     this.type = type;
     this.id = id;
     this.transformMatrix = transformMatrix;
     this.surfaceTextureHelper = surfaceTextureHelper;
-    this.releaseCallback = releaseCallback;
-    this.refCount = 1; // Creator implicitly holds a reference.
+    this.refCountDelegate = new RefCountDelegate(releaseCallback);
   }
 
   @Override
@@ -72,18 +71,12 @@ class TextureBufferImpl implements VideoFrame.TextureBuffer {
 
   @Override
   public void retain() {
-    synchronized (refCountLock) {
-      ++refCount;
-    }
+    refCountDelegate.retain();
   }
 
   @Override
   public void release() {
-    synchronized (refCountLock) {
-      if (--refCount == 0 && releaseCallback != null) {
-        releaseCallback.run();
-      }
-    }
+    refCountDelegate.release();
   }
 
   @Override