Prepare for removal of source_filter.gypi:

runtime/platform/floating_point_win.cc

Index: runtime/platform/floating_point_win.cc
===================================================================
--- runtime/platform/floating_point_win.cc	(revision 18775)
+++ runtime/platform/floating_point_win.cc	(working copy)
@@ -2,11 +2,12 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-#include <math.h>
-#include <limits>
-
 #include "platform/globals.h"
+#if defined(TARGET_OS_WINDOWS)
 
+#include <math.h>  // NOLINT
+#include <limits>  // NOLINT
+
 // Taken from third_party/v8/src/platform-win32.cc
 double fmod_ieee(double x, double y) {
   // x is dividend, y is divisor.
@@ -44,3 +45,5 @@
     return atan2(x, y);
   }
 }
+
+#endif  // defined(TARGET_OS_WINDOWS)