Deleted OS_WIN and all Windows specific files from base.

base/bind_helpers.h

Index: base/bind_helpers.h
diff --git a/base/bind_helpers.h b/base/bind_helpers.h
index 24063ad1ce58fd27c5535ec81c294c597db841df..d0c867444b33adb83b782cd53f9693bcf2fcb72b 100644
--- a/base/bind_helpers.h
+++ b/base/bind_helpers.h
@@ -229,18 +229,8 @@ class SupportsAddRefAndRelease {
     void AddRef();
   };
 
-// MSVC warns when you try to use Base if T has a private destructor, the
-// common pattern for refcounted types. It does this even though no attempt to
-// instantiate Base is made.  We disable the warning for this definition.
-#if defined(OS_WIN)
-#pragma warning(push)
-#pragma warning(disable:4624)
-#endif
   struct Base : public T, public BaseMixin {
   };
-#if defined(OS_WIN)
-#pragma warning(pop)
-#endif
 
   template <void(BaseMixin::*)(void)> struct Helper {};