EDK: Some more scoped_ptr -> std::unique_ptr conversions.

After this, the remaining conversions in //mojo/edk/system are all for
scoped_ptr<MessageInTransit> (I think), and there are (semi)public API changes
in //mojo/edk/embedder.

R=vardhan@google.com

Review URL: https://codereview.chromium.org/1350503005 .
diff --git a/mojo/edk/system/channel_test_base.cc b/mojo/edk/system/channel_test_base.cc
index c1bf173..df90d3a 100644
--- a/mojo/edk/system/channel_test_base.cc
+++ b/mojo/edk/system/channel_test_base.cc
@@ -4,6 +4,8 @@
 
 #include "mojo/edk/system/channel_test_base.h"
 
+#include <utility>
+
 #include "base/logging.h"
 #include "base/message_loop/message_loop.h"
 #include "mojo/edk/embedder/platform_channel_pair.h"
@@ -35,7 +37,7 @@
 
   CHECK(raw_channels_[i]);
   CHECK(channels_[i]);
-  channels_[i]->Init(raw_channels_[i].Pass());
+  channels_[i]->Init(std::move(raw_channels_[i]));
 }
 
 void ChannelTestBase::CreateAndInitChannelOnIOThread(unsigned i) {