Replace the remaining scoped_ptr with unique_ptr in webrtc/modules/

(This is a re-land of https://codereview.webrtc.org/1921233002, which
got reverted for breaking Chromium.)

BUG=webrtc:5520

Review URL: https://codereview.webrtc.org/1923133002

Cr-Commit-Position: refs/heads/master@{#12522}
diff --git a/webrtc/modules/utility/source/process_thread_impl.cc b/webrtc/modules/utility/source/process_thread_impl.cc
index 8cdf016..68c7ab6 100644
--- a/webrtc/modules/utility/source/process_thread_impl.cc
+++ b/webrtc/modules/utility/source/process_thread_impl.cc
@@ -36,9 +36,9 @@
 ProcessThread::~ProcessThread() {}
 
 // static
-rtc::scoped_ptr<ProcessThread> ProcessThread::Create(
+std::unique_ptr<ProcessThread> ProcessThread::Create(
     const char* thread_name) {
-  return rtc::scoped_ptr<ProcessThread>(new ProcessThreadImpl(thread_name));
+  return std::unique_ptr<ProcessThread>(new ProcessThreadImpl(thread_name));
 }
 
 ProcessThreadImpl::ProcessThreadImpl(const char* thread_name)
@@ -119,7 +119,7 @@
   wake_up_->Set();
 }
 
-void ProcessThreadImpl::PostTask(rtc::scoped_ptr<ProcessTask> task) {
+void ProcessThreadImpl::PostTask(std::unique_ptr<ProcessTask> task) {
   // Allowed to be called on any thread.
   {
     rtc::CritScope lock(&lock_);