Ensure VideoCaptureSystem is deleted on the right thread

InProcessVideoCaptureProvider uses VideoCaptureSystem on a separate
device thread, but it was deleting it on the IO browser thread. Fixed
InProcessVideoCaptureProvider to delete VideoCaptureSystem on the same
thread on which it's being used.

Bug: 1127447
Change-Id: Ibf867acea96a28dd992ae9d1139a5ec162d8ee8d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2427031
Commit-Queue: Sergey Ulanov <sergeyu@chromium.org>
Auto-Submit: Sergey Ulanov <sergeyu@chromium.org>
Reviewed-by: Guido Urdaneta <guidou@chromium.org>
Cr-Commit-Position: refs/heads/master@{#811551}

content/browser/renderer_host/media/in_process_video_capture_provider.cc

@@ -23,6 +23,11 @@ InProcessVideoCaptureProvider::InProcessVideoCaptureProvider(
 
 InProcessVideoCaptureProvider::~InProcessVideoCaptureProvider() {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
+
+  if (video_capture_system_ && !device_task_runner_->BelongsToCurrentThread()) {
+    device_task_runner_->DeleteSoon(FROM_HERE,
+                                    std::move(video_capture_system_));
+  }
 }
 
 // static

content/browser/renderer_host/media/in_process_video_capture_provider.h

@@ -38,7 +38,7 @@ class CONTENT_EXPORT InProcessVideoCaptureProvider
 
  private:
   // Can be nullptr.
-  const std::unique_ptr<media::VideoCaptureSystem> video_capture_system_;
+  std::unique_ptr<media::VideoCaptureSystem> video_capture_system_;
   // The message loop of media stream device thread, where VCD's live.
   const scoped_refptr<base::SingleThreadTaskRunner> device_task_runner_;
   base::RepeatingCallback<void(const std::string&)> emit_log_message_cb_;

content/browser/renderer_host/media/video_capture_manager_unittest.cc

@@ -280,7 +280,7 @@ class VideoCaptureManagerTest : public testing::Test {
     ASSERT_GE(devices_.size(), 2u);
   }
 
-  void TearDown() override {}
+  void TearDown() override { task_environment_.RunUntilIdle(); }
 
   void OnGotControllerCallback(
       VideoCaptureControllerID id,
@@ -348,12 +348,12 @@ class VideoCaptureManagerTest : public testing::Test {
   }
 #endif
 
+  BrowserTaskEnvironment task_environment_;
   ScreenlockMonitorTestSource* screenlock_monitor_source_;
   std::unique_ptr<ScreenlockMonitor> screenlock_monitor_;
   std::map<VideoCaptureControllerID, VideoCaptureController*> controllers_;
   scoped_refptr<VideoCaptureManager> vcm_;
   std::unique_ptr<MockMediaStreamProviderListener> listener_;
-  BrowserTaskEnvironment task_environment_;
   std::unique_ptr<MockFrameObserver> frame_observer_;
   WrappedDeviceFactory* video_capture_device_factory_;
   blink::MediaStreamDevices devices_;