Use the location where FileDescriptorWatcher is created to track the libevent handlers

base/message_loop/message_pump_libevent.h

Index: base/message_loop/message_pump_libevent.h
diff --git a/base/message_loop/message_pump_libevent.h b/base/message_loop/message_pump_libevent.h
index 752dc929a04f3014869f0a66bc47faed52df3224..1124560d66c1c8ae910a7b86cf592477f85cdf7e 100644
--- a/base/message_loop/message_pump_libevent.h
+++ b/base/message_loop/message_pump_libevent.h
@@ -6,6 +6,7 @@
 #define BASE_MESSAGE_LOOP_MESSAGE_PUMP_LIBEVENT_H_
 
 #include "base/compiler_specific.h"
+#include "base/location.h"
 #include "base/macros.h"
 #include "base/message_loop/message_pump.h"
 #include "base/threading/thread_checker.h"
@@ -37,7 +38,7 @@ class BASE_EXPORT MessagePumpLibevent : public MessagePump {
   // Object returned by WatchFileDescriptor to manage further watching.
   class FileDescriptorWatcher {
    public:
-    FileDescriptorWatcher();
+    explicit FileDescriptorWatcher(const tracked_objects::Location& from_here);
     ~FileDescriptorWatcher();  // Implicitly calls StopWatchingFileDescriptor.
 
     // NOTE: These methods aren't called StartWatching()/StopWatching() to
@@ -47,6 +48,10 @@ class BASE_EXPORT MessagePumpLibevent : public MessagePump {
     // to do.
     bool StopWatchingFileDescriptor();
 
+    const tracked_objects::Location& created_from_location() {
+      return created_from_location_;
+    }
+
    private:
     friend class MessagePumpLibevent;
     friend class MessagePumpLibeventTest;
@@ -73,6 +78,8 @@ class BASE_EXPORT MessagePumpLibevent : public MessagePump {
     // destructor.
     bool* was_destroyed_;
 
+    const tracked_objects::Location created_from_location_;
+
     DISALLOW_COPY_AND_ASSIGN(FileDescriptorWatcher);
   };