EDK: Move mutex.*, cond_var.*, and thread_annotations.h to //mojo/edk/util.

mojo/edk/system/endpoint_relayer.h

Index: mojo/edk/system/endpoint_relayer.h
diff --git a/mojo/edk/system/endpoint_relayer.h b/mojo/edk/system/endpoint_relayer.h
index 036eaa3a50594f6742ca762f16756ae958a48e59..bb06894149d155e78466419e2df7b9f1507ac09a 100644
--- a/mojo/edk/system/endpoint_relayer.h
+++ b/mojo/edk/system/endpoint_relayer.h
@@ -8,8 +8,9 @@
 #include <memory>
 
 #include "mojo/edk/system/channel_endpoint_client.h"
-#include "mojo/edk/system/mutex.h"
+#include "mojo/edk/util/mutex.h"
 #include "mojo/edk/util/ref_ptr.h"
+#include "mojo/edk/util/thread_annotations.h"
 #include "mojo/public/cpp/system/macros.h"
 
 namespace mojo {
@@ -84,7 +85,7 @@ class EndpointRelayer final : public ChannelEndpointClient {
   EndpointRelayer();
   ~EndpointRelayer() override;
 
-  Mutex mutex_;
+  util::Mutex mutex_;
   util::RefPtr<ChannelEndpoint> endpoints_[2] MOJO_GUARDED_BY(mutex_);
   std::unique_ptr<Filter> filter_ MOJO_GUARDED_BY(mutex_);