Reland "EDK: Move //mojo/edk/system/waitable_event* to 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 420d0b85cafed6cf3c1febb7b4f93861f7f01760..f2296ffd704642394b1ae7a10b17d3ad691342ac 100644
--- a/mojo/edk/system/test_channel_endpoint_client.h
+++ b/mojo/edk/system/test_channel_endpoint_client.h
@@ -16,10 +16,12 @@
 #include "mojo/public/cpp/system/macros.h"
 
 namespace mojo {
-namespace system {
 
+namespace util {
 class ManualResetWaitableEvent;
+}
 
+namespace system {
 namespace test {
 
 class TestChannelEndpointClient final : public ChannelEndpointClient {
@@ -41,7 +43,7 @@ class TestChannelEndpointClient final : public ChannelEndpointClient {
 
   // Sets an event to signal when we receive a message. (|read_event| must live
   // until this object is destroyed or the read event is reset to null.)
-  void SetReadEvent(ManualResetWaitableEvent* read_event);
+  void SetReadEvent(util::ManualResetWaitableEvent* read_event);
 
   // |ChannelEndpointClient| implementation:
   bool OnReadMessage(unsigned port, MessageInTransit* message) override;
@@ -61,7 +63,7 @@ class TestChannelEndpointClient final : public ChannelEndpointClient {
   MessageInTransitQueue messages_ MOJO_GUARDED_BY(mutex_);
 
   // Event to trigger if we read a message (may be null).
-  ManualResetWaitableEvent* read_event_ MOJO_GUARDED_BY(mutex_);
+  util::ManualResetWaitableEvent* read_event_ MOJO_GUARDED_BY(mutex_);
 
   MOJO_DISALLOW_COPY_AND_ASSIGN(TestChannelEndpointClient);
 };