Revert to repair UI test bustage

base/message_pump_win.cc

Index: base/message_pump_win.cc
===================================================================
--- base/message_pump_win.cc	(revision 6915)
+++ base/message_pump_win.cc	(working copy)
@@ -380,19 +380,13 @@
          msg.hwnd != message_hwnd_);
 
   // Since we discarded a kMsgHaveWork message, we must update the flag.
-  int old_have_work = InterlockedExchange(&have_work_, 0);
-  DCHECK(old_have_work);
+  InterlockedExchange(&have_work_, 0);
 
-  // We don't need a special time slice if we didn't have_message to process. 
-  if (!have_message)
-    return false;
+  // TODO(darin,jar): There is risk of being lost in a sub-pump within the call
+  // to ProcessMessageHelper, which could result in no longer getting a
+  // kMsgHaveWork message until the next out-of-band call to ScheduleWork.
 
-  // Guarantee we'll get another time slice in the case where we go into native
-  // windows code.   This ScheduleWork() may hurt performance a tiny bit when
-  // tasks appear very infrequently, but when the event queue is busy, the
-  // kMsgHaveWork events get (percentage wise) rarer and rarer.
-  ScheduleWork();
-  return ProcessMessageHelper(msg);
+  return have_message && ProcessMessageHelper(msg);
 }
 
 //-----------------------------------------------------------------------------