Revert making HandleWatcher block until no longer waiting on pipe (r285266).

mojo/message_pump/handle_watcher.h

Index: mojo/message_pump/handle_watcher.h
diff --git a/mojo/message_pump/handle_watcher.h b/mojo/message_pump/handle_watcher.h
index 1dc079ed6b239ba4bbba4f633ce7ed1a63185888..5bb3adb07761cb49943406beb111156205bbb375 100644
--- a/mojo/message_pump/handle_watcher.h
+++ b/mojo/message_pump/handle_watcher.h
@@ -28,7 +28,6 @@ class MOJO_MESSAGE_PUMP_EXPORT HandleWatcher {
  public:
   HandleWatcher();
 
-  // The destructor implicitly stops listening. See Stop() for details.
   ~HandleWatcher();
 
   // Starts listening for |handle|. This implicitly invokes Stop(). In other
@@ -43,8 +42,7 @@ class MOJO_MESSAGE_PUMP_EXPORT HandleWatcher {
              MojoDeadline deadline,
              const base::Callback<void(MojoResult)>& callback);
 
-  // Stops listening. Does nothing if not in the process of listening. Blocks
-  // until no longer listening on the handle.
+  // Stops listening. Does nothing if not in the process of listening.
   void Stop();
 
  private: