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

mojo/edk/system/channel_manager.h

Index: mojo/edk/system/channel_manager.h
diff --git a/mojo/edk/system/channel_manager.h b/mojo/edk/system/channel_manager.h
index da3f2924376baed5ba0cd57cbb22a35aec8ad8aa..1ef217b8e5deab71933c1edd09fb3c85c98514c9 100644
--- a/mojo/edk/system/channel_manager.h
+++ b/mojo/edk/system/channel_manager.h
@@ -13,8 +13,9 @@
 #include "mojo/edk/embedder/platform_task_runner.h"
 #include "mojo/edk/embedder/scoped_platform_handle.h"
 #include "mojo/edk/system/channel_id.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 base {
@@ -152,7 +153,7 @@ class ChannelManager {
   // TODO(vtl): Annotate the above rule using |MOJO_ACQUIRED_{BEFORE,AFTER}()|,
   // once clang actually checks such annotations.
   // https://github.com/domokit/mojo/issues/313
-  mutable Mutex mutex_;
+  mutable util::Mutex mutex_;
 
   using ChannelIdToChannelMap =
       std::unordered_map<ChannelId, util::RefPtr<Channel>>;