Mojo: Move system embedder API files to mojo/system/embedder.

mojo/system/embedder/platform_channel_pair.h

Index: mojo/system/embedder/platform_channel_pair.h
diff --git a/mojo/system/platform_channel_pair.h b/mojo/system/embedder/platform_channel_pair.h
similarity index 92%
rename from mojo/system/platform_channel_pair.h
rename to mojo/system/embedder/platform_channel_pair.h
index 41ca32f791ce4d2cf7bd606f66b194f1bd32f901..36e3877a37cf10e4f050caa783c57ecc2fc2ab72 100644
--- a/mojo/system/platform_channel_pair.h
+++ b/mojo/system/embedder/platform_channel_pair.h
@@ -2,13 +2,13 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef MOJO_SYSTEM_PLATFORM_CHANNEL_PAIR_H_
-#define MOJO_SYSTEM_PLATFORM_CHANNEL_PAIR_H_
+#ifndef MOJO_SYSTEM_EMBEDDER_PLATFORM_CHANNEL_PAIR_H_
+#define MOJO_SYSTEM_EMBEDDER_PLATFORM_CHANNEL_PAIR_H_
 
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/process/launch.h"
-#include "mojo/system/scoped_platform_handle.h"
+#include "mojo/system/embedder/scoped_platform_handle.h"
 #include "mojo/system/system_impl_export.h"
 
 class CommandLine;
@@ -70,4 +70,4 @@ class MOJO_SYSTEM_IMPL_EXPORT PlatformChannelPair {
 }  // namespace embedder
 }  // namespace mojo
 
-#endif  // MOJO_SYSTEM_PLATFORM_CHANNEL_PAIR_H_
+#endif  // MOJO_SYSTEM_EMBEDDER_PLATFORM_CHANNEL_PAIR_H_