Create new 'skia_os' variable to replace use of 'OS' in most places.
http://codereview.appspot.com/4627085



git-svn-id: http://skia.googlecode.com/svn/trunk@1782 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gyp/FileReaderApp.gyp b/gyp/FileReaderApp.gyp
index 2db992f..0e2c48f 100644
--- a/gyp/FileReaderApp.gyp
+++ b/gyp/FileReaderApp.gyp
@@ -30,7 +30,7 @@
       ],
       'conditions' : [
         # Only supports Mac currently
-        ['OS == "mac"', {
+        ['skia_os == "mac"', {
           'sources': [
             '../experimental/SimpleCocoaApp/SkNSWindow.mm',
             '../experimental/SimpleCocoaApp/SkNSView.mm',