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

mojo/edk/system/test_channel_endpoint_client.h

Index: mojo/edk/system/test_channel_endpoint_client.h
diff --git a/mojo/edk/system/test_channel_endpoint_client.h b/mojo/edk/system/test_channel_endpoint_client.h
index df044606668ffc50403b4a5e6761c5c8d924bbb1..420d0b85cafed6cf3c1febb7b4f93861f7f01760 100644
--- a/mojo/edk/system/test_channel_endpoint_client.h
+++ b/mojo/edk/system/test_channel_endpoint_client.h
@@ -10,8 +10,9 @@
 #include "mojo/edk/system/channel_endpoint.h"
 #include "mojo/edk/system/channel_endpoint_client.h"
 #include "mojo/edk/system/message_in_transit_queue.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 {
@@ -52,7 +53,7 @@ class TestChannelEndpointClient final : public ChannelEndpointClient {
   TestChannelEndpointClient();
   ~TestChannelEndpointClient() override;
 
-  mutable Mutex mutex_;
+  mutable util::Mutex mutex_;
 
   unsigned port_ MOJO_GUARDED_BY(mutex_);
   util::RefPtr<ChannelEndpoint> endpoint_ MOJO_GUARDED_BY(mutex_);