Change destruction order to fix potential invalid pointer dereference.

BUG=657226

Review-Url: https://codereview.webrtc.org/2450953002
Cr-Original-Commit-Position: refs/heads/master@{#14792}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 54b0acb432b3cd4a20403862e2ed3ef33ae85c0f
diff --git a/modules/desktop_capture/screen_capturer_mac.mm b/modules/desktop_capture/screen_capturer_mac.mm
index 47885ee..3251e5a 100644
--- a/modules/desktop_capture/screen_capturer_mac.mm
+++ b/modules/desktop_capture/screen_capturer_mac.mm
@@ -390,8 +390,8 @@
 
 ScreenCapturerMac::~ScreenCapturerMac() {
   ReleaseBuffers();
-  display_stream_manager_->PrepareForSelfDestruction();
   UnregisterRefreshAndMoveHandlers();
+  display_stream_manager_->PrepareForSelfDestruction();
   dlclose(app_services_library_);
   dlclose(opengl_library_);
 }