Revert of Use Mojo pipes to signal sync IPC events

mojo/public/cpp/bindings/lib/sync_handle_registry.cc

Index: mojo/public/cpp/bindings/lib/sync_handle_registry.cc
diff --git a/mojo/public/cpp/bindings/lib/sync_handle_registry.cc b/mojo/public/cpp/bindings/lib/sync_handle_registry.cc
index f6372d9eb51d6ecb0df89807b8abc045a90587c9..e4b495579377fe4297f7639a40f2990fe27f303a 100644
--- a/mojo/public/cpp/bindings/lib/sync_handle_registry.cc
+++ b/mojo/public/cpp/bindings/lib/sync_handle_registry.cc
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "mojo/public/cpp/bindings/sync_handle_registry.h"
+#include "mojo/public/cpp/bindings/lib/sync_handle_registry.h"
 
 #include "base/lazy_instance.h"
 #include "base/logging.h"
@@ -11,6 +11,7 @@
 #include "mojo/public/c/system/core.h"
 
 namespace mojo {
+namespace internal {
 namespace {
 
 base::LazyInstance<base::ThreadLocalPointer<SyncHandleRegistry>>
@@ -110,4 +111,5 @@
   g_current_sync_handle_watcher.Pointer()->Set(nullptr);
 }
 
+}  // namespace internal
 }  // namespace mojo