Prep work for win7-specific condition variable

base/synchronization/condition_variable.h

Index: base/synchronization/condition_variable.h
===================================================================
--- base/synchronization/condition_variable.h	(revision 113067)
+++ base/synchronization/condition_variable.h	(working copy)
@@ -68,9 +68,7 @@
 
 #include "build/build_config.h"
 
-#if defined(OS_WIN)
-#include <windows.h>
-#elif defined(OS_POSIX)
+#if defined(OS_POSIX)
 #include <pthread.h>
 #endif
 
@@ -80,6 +78,7 @@
 
 namespace base {
 
+class ConditionVarImpl;
 class TimeDelta;
 
 class BASE_EXPORT ConditionVariable {
@@ -102,78 +101,8 @@
  private:
 
 #if defined(OS_WIN)
-
-  // Define Event class that is used to form circularly linked lists.
-  // The list container is an element with NULL as its handle_ value.
-  // The actual list elements have a non-zero handle_ value.
-  // All calls to methods MUST be done under protection of a lock so that links
-  // can be validated.  Without the lock, some links might asynchronously
-  // change, and the assertions would fail (as would list change operations).
-  class Event {
-   public:
-    // Default constructor with no arguments creates a list container.
-    Event();
-    ~Event();
-
-    // InitListElement transitions an instance from a container, to an element.
-    void InitListElement();
-
-    // Methods for use on lists.
-    bool IsEmpty() const;
-    void PushBack(Event* other);
-    Event* PopFront();
-    Event* PopBack();
-
-    // Methods for use on list elements.
-    // Accessor method.
-    HANDLE handle() const;
-    // Pull an element from a list (if it's in one).
-    Event* Extract();
-
-    // Method for use on a list element or on a list.
-    bool IsSingleton() const;
-
-   private:
-    // Provide pre/post conditions to validate correct manipulations.
-    bool ValidateAsDistinct(Event* other) const;
-    bool ValidateAsItem() const;
-    bool ValidateAsList() const;
-    bool ValidateLinks() const;
-
-    HANDLE handle_;
-    Event* next_;
-    Event* prev_;
-    DISALLOW_COPY_AND_ASSIGN(Event);
-  };
-
-  // Note that RUNNING is an unlikely number to have in RAM by accident.
-  // This helps with defensive destructor coding in the face of user error.
-  enum RunState { SHUTDOWN = 0, RUNNING = 64213 };
-
-  // Internal implementation methods supporting Wait().
-  Event* GetEventForWaiting();
-  void RecycleEvent(Event* used_event);
-
-  RunState run_state_;
-
-  // Private critical section for access to member data.
-  base::Lock internal_lock_;
-
-  // Lock that is acquired before calling Wait().
-  base::Lock& user_lock_;
-
-  // Events that threads are blocked on.
-  Event waiting_list_;
-
-  // Free list for old events.
-  Event recycling_list_;
-  int recycling_list_size_;
-
-  // The number of allocated, but not yet deleted events.
-  int allocation_counter_;
-
+  ConditionVarImpl* impl_;
 #elif defined(OS_POSIX)
-
   pthread_cond_t condition_;
   pthread_mutex_t* user_mutex_;
 #if !defined(NDEBUG)