Add an explicit ObjectWatcher::IsWatching() method

base/win/object_watcher.h

Index: base/win/object_watcher.h
diff --git a/base/win/object_watcher.h b/base/win/object_watcher.h
index bf7f8b3e92c2860ceabb2c245b94135bf949b047..ecd0415d5d068ebf3da6a061c1c0f6651e54edf9 100644
--- a/base/win/object_watcher.h
+++ b/base/win/object_watcher.h
@@ -74,9 +74,11 @@ class BASE_EXPORT ObjectWatcher : public MessageLoop::DestructionObserver {
   //
   bool StopWatching();
 
-  // Returns the handle of the object being watched, or NULL if the object
-  // watcher is stopped.
-  HANDLE GetWatchedObject();
+  // Returns true if currently watching an object.
+  bool IsWatching() const;
+
+  // Returns the handle of the object being watched.
+  HANDLE GetWatchedObject() const;
 
  private:
   // Called on a background thread when done waiting.