Revert of Replace the remaining scoped_ptr with unique_ptr in webrtc/modules/ (patchset #1 id:40001 of https://codereview.webrtc.org/1921233002/ )

Reason for revert:
Fails on Chromium FYI bots.

https://build.chromium.org/p/chromium.webrtc.fyi/builders/Linux%20Builder/builds/5392/

Original issue's description:
> Replace the remaining scoped_ptr with unique_ptr in webrtc/modules/
>
> BUG=webrtc:5520
>
> Committed: https://crrev.com/2c27a062ee46258abe9facc2cceee74f09bf6a99
> Cr-Commit-Position: refs/heads/master@{#12511}

TBR=tommi@webrtc.org,kwiberg@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=webrtc:5520

Review URL: https://codereview.webrtc.org/1924443002

Cr-Commit-Position: refs/heads/master@{#12513}
diff --git a/webrtc/modules/utility/source/process_thread_impl.h b/webrtc/modules/utility/source/process_thread_impl.h
index 330aec9..2855ed9 100644
--- a/webrtc/modules/utility/source/process_thread_impl.h
+++ b/webrtc/modules/utility/source/process_thread_impl.h
@@ -33,7 +33,7 @@
   void Stop() override;
 
   void WakeUp(Module* module) override;
-  void PostTask(std::unique_ptr<ProcessTask> task) override;
+  void PostTask(rtc::scoped_ptr<ProcessTask> task) override;
 
   void RegisterModule(Module* module) override;
   void DeRegisterModule(Module* module) override;