Replace the remaining scoped_ptr with unique_ptr in webrtc/modules/

BUG=webrtc:5520

Review URL: https://codereview.webrtc.org/1921233002

Cr-Commit-Position: refs/heads/master@{#12511}

webrtc/modules/rtp_rtcp/source/receive_statistics_unittest.cc

@@ -8,9 +8,10 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
+#include <memory>
+
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
-#include "webrtc/base/scoped_ptr.h"
 #include "webrtc/modules/rtp_rtcp/include/receive_statistics.h"
 #include "webrtc/system_wrappers/include/clock.h"
 
@@ -36,7 +37,7 @@ class ReceiveStatisticsTest : public ::testing::Test {
 
  protected:
   SimulatedClock clock_;
-  rtc::scoped_ptr<ReceiveStatistics> receive_statistics_;
+  std::unique_ptr<ReceiveStatistics> receive_statistics_;
   RTPHeader header1_;
   RTPHeader header2_;
 };