Replace scoped_ptr with unique_ptr in webrtc/base/

This propagated into various other places. Also had to #include headers that
were implicitly pulled by "scoped_ptr.h".

BUG=webrtc:5520

Review URL: https://codereview.webrtc.org/1920043002

Cr-Commit-Position: refs/heads/master@{#12501}
diff --git a/webrtc/base/natserver.cc b/webrtc/base/natserver.cc
index b071e01..222d270 100644
--- a/webrtc/base/natserver.cc
+++ b/webrtc/base/natserver.cc
@@ -8,6 +8,8 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
+#include <memory>
+
 #include "webrtc/base/natsocketfactory.h"
 #include "webrtc/base/natserver.h"
 #include "webrtc/base/logging.h"
@@ -195,7 +197,7 @@
 
   // Forward this packet to the internal address.
   // First prepend the address in a quasi-STUN format.
-  scoped_ptr<char[]> real_buf(new char[size + kNATEncodedIPv6AddressSize]);
+  std::unique_ptr<char[]> real_buf(new char[size + kNATEncodedIPv6AddressSize]);
   size_t addrlength = PackAddressForNAT(real_buf.get(),
                                         size + kNATEncodedIPv6AddressSize,
                                         remote_addr);