Base: First pass at having base.dll: definition of

base/synchronization/waitable_event.h

Index: base/synchronization/waitable_event.h
===================================================================
--- base/synchronization/waitable_event.h	(revision 78949)
+++ base/synchronization/waitable_event.h	(working copy)
@@ -6,6 +6,7 @@
 #define BASE_SYNCHRONIZATION_WAITABLE_EVENT_H_
 #pragma once
 
+#include "base/base_api.h"
 #include "base/basictypes.h"
 
 #if defined(OS_WIN)
@@ -41,7 +42,7 @@
 // by a Windows event object.  This is intentional.  If you are writing Windows
 // specific code and you need other features of a Windows event, then you might
 // be better off just using an Windows event directly.
-class WaitableEvent {
+class BASE_API WaitableEvent {
  public:
   // If manual_reset is true, then to set the event state to non-signaled, a
   // consumer must call the Reset method.  If this parameter is false, then the