replace platform conditions with os_posix and os_bsd where applicable

content/content_plugin.gypi

Index: content/content_plugin.gypi
diff --git a/content/content_plugin.gypi b/content/content_plugin.gypi
index 734c4976a0d2cfcfd6013443c73ee6297f6ff79b..cab0b488d282b6546b0e6e9674940013e2b26476 100644
--- a/content/content_plugin.gypi
+++ b/content/content_plugin.gypi
@@ -34,7 +34,7 @@
   # These are layered in conditionals in the event other platforms
   # end up using this module as well.
   'conditions': [
-    ['OS=="openbsd"', {
+    ['os_bsd==1', {
       'sources/': [
         ['exclude', '^plugin/plugin_main_linux\\.cc$'],
       ],