Reland "EDK: Move //mojo/edk/system/waitable_event* to edk/util."

mojo/edk/util/mutex_unittest.cc

Index: mojo/edk/util/mutex_unittest.cc
diff --git a/mojo/edk/util/mutex_unittest.cc b/mojo/edk/util/mutex_unittest.cc
index 6730aba7ee586513a6187292b1b1b10f9188859a..7e8aff8e1e620c2debfc44850a181193c6f4f794 100644
--- a/mojo/edk/util/mutex_unittest.cc
+++ b/mojo/edk/util/mutex_unittest.cc
@@ -11,13 +11,15 @@
 #include "mojo/edk/system/test/sleep.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
+using mojo::system::test::SleepMilliseconds;
+
 namespace mojo {
 namespace util {
 namespace {
 
 // Sleeps for a "very small" amount of time.
 void EpsilonRandomSleep() {
-  system::test::SleepMilliseconds(static_cast<unsigned>(rand()) % 20u);
+  SleepMilliseconds(static_cast<unsigned>(rand()) % 20u);
 }
 
 // Basic test to make sure that Lock()/Unlock()/TryLock() don't crash ----------