From 53d712402f713d9bdbb0fa928442a19ffa14d5d3 Mon Sep 17 00:00:00 2001
From: Gian-Carlo Pascutto <gcp@mozilla.com>
Date: Tue, 28 Jul 2015 08:55:06 +0200
Subject: [PATCH] Bug 1186657. r=jesup,nchen

---
 .../org/webrtc/videoengine/VideoCaptureAndroid.java  | 11 ++++++++++-
 .../video_capture/android/video_capture_android.cc   | 12 +++++++++++-
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/media/webrtc/trunk/webrtc/modules/video_capture/android/java/src/org/webrtc/videoengine/VideoCaptureAndroid.java b/media/webrtc/trunk/webrtc/modules/video_capture/android/java/src/org/webrtc/videoengine/VideoCaptureAndroid.java
index 2c67e743d19..c7729c4794a 100644
--- a/media/webrtc/trunk/webrtc/modules/video_capture/android/java/src/org/webrtc/videoengine/VideoCaptureAndroid.java
+++ b/media/webrtc/trunk/webrtc/modules/video_capture/android/java/src/org/webrtc/videoengine/VideoCaptureAndroid.java
@@ -56,7 +56,7 @@ public class VideoCaptureAndroid implements PreviewCallback, Callback, AppStateL
   private Handler cameraThreadHandler;
   private Context context;
   private final int id;
-  private final long native_capturer;  // |VideoCaptureAndroid*| in C++.
+  private volatile long native_capturer;  // |VideoCaptureAndroid*| in C++.
   private SurfaceTexture cameraSurfaceTexture;
   private int[] cameraGlTextures = null;
 
@@ -373,6 +373,15 @@ public class VideoCaptureAndroid implements PreviewCallback, Callback, AppStateL
     return status;
   }
 
+  @WebRTCJNITarget
+  private void unlinkCapturer() {
+    // stopCapture might fail. That might leave the callbacks dangling, so make
+    // sure those don't call into dead code.
+    // Note that onPreviewCameraFrame isn't synchronized, so there's no point in
+    // synchronizing us either. ProvideCameraFrame has to do the null check.
+    native_capturer = 0;
+  }
+
   private void stopCaptureOnCameraThread(
       Exchanger<Boolean> result) {
     if (camera == null) {
diff --git a/media/webrtc/trunk/webrtc/modules/video_capture/android/video_capture_android.cc b/media/webrtc/trunk/webrtc/modules/video_capture/android/video_capture_android.cc
index 4df1efb19da..ad784c7cea9 100644
--- a/media/webrtc/trunk/webrtc/modules/video_capture/android/video_capture_android.cc
+++ b/media/webrtc/trunk/webrtc/modules/video_capture/android/video_capture_android.cc
@@ -41,6 +41,8 @@ void JNICALL ProvideCameraFrame(
     jint rotation,
     jlong timeStamp,
     jlong context) {
+  if (!context)
+    return;
   webrtc::videocapturemodule::VideoCaptureAndroid* captureModule =
       reinterpret_cast<webrtc::videocapturemodule::VideoCaptureAndroid*>(
           context);
@@ -167,7 +169,14 @@ VideoCaptureAndroid::~VideoCaptureAndroid() {
   if (_captureStarted)
     StopCapture();
   AttachThreadScoped ats(g_jvm);
-  ats.env()->DeleteGlobalRef(_jCapturer);
+  JNIEnv* env = ats.env();
+
+  // Avoid callbacks into ourself even if the above stopCapture fails.
+  jmethodID j_unlink =
+    env->GetMethodID(g_java_capturer_class, "unlinkCapturer", "()V");
+  env->CallVoidMethod(_jCapturer, j_unlink);
+
+  env->DeleteGlobalRef(_jCapturer);
 }
 
 int32_t VideoCaptureAndroid::StartCapture(
@@ -216,6 +225,7 @@ int32_t VideoCaptureAndroid::StopCapture() {
   // onIncomingFrame() call.
   _apiCs.Leave();
 
+  // try to stop the capturer.
   jmethodID j_stop =
       env->GetMethodID(g_java_capturer_class, "stopCapture", "()Z");
   return env->CallBooleanMethod(_jCapturer, j_stop) ? 0 : -1;