Move PlatformChannelPair to //mojo/edk/platform and rename it PlatformPipe.

mojo/edk/system/data_pipe_impl_unittest.cc

Index: mojo/edk/system/data_pipe_impl_unittest.cc
diff --git a/mojo/edk/system/data_pipe_impl_unittest.cc b/mojo/edk/system/data_pipe_impl_unittest.cc
index f161f3410da1e4ba4f872227cfd5eae5bd6e7f00..4e57645df3b114039511b198395a80e0197426dc 100644
--- a/mojo/edk/system/data_pipe_impl_unittest.cc
+++ b/mojo/edk/system/data_pipe_impl_unittest.cc
@@ -13,8 +13,8 @@
 #include <utility>
 
 #include "base/logging.h"
-#include "mojo/edk/embedder/platform_channel_pair.h"
 #include "mojo/edk/embedder/simple_platform_support.h"
+#include "mojo/edk/platform/platform_pipe.h"
 #include "mojo/edk/platform/thread_utils.h"
 #include "mojo/edk/system/channel.h"
 #include "mojo/edk/system/channel_endpoint.h"
@@ -31,6 +31,7 @@
 #include "mojo/public/cpp/system/macros.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
+using mojo::platform::PlatformPipe;
 using mojo::platform::ThreadSleep;
 using mojo::util::MakeRefCounted;
 using mojo::util::RefPtr;
@@ -320,7 +321,7 @@ class RemoteDataPipeImplTestHelper : public DataPipeImplTestHelper {
                        RefPtr<ChannelEndpoint>&& ep1) {
     CHECK(io_thread_.IsCurrentAndRunning());
 
-    embedder::PlatformChannelPair channel_pair;
+    PlatformPipe channel_pair;
     channels_[0] = MakeRefCounted<Channel>(&platform_support_);
     channels_[0]->Init(io_thread_.task_runner().Clone(),
                        io_thread_.platform_handle_watcher(),