Change the platform app manifest structure.

chrome/common/extensions/docs/build/directory.py

Index: chrome/common/extensions/docs/build/directory.py
diff --git a/chrome/common/extensions/docs/build/directory.py b/chrome/common/extensions/docs/build/directory.py
index 9e2627e985d74e038497b1ceff63efeb2a86b414..b7522f02dc8ab33b7c84b20609903f099bba4968 100644
--- a/chrome/common/extensions/docs/build/directory.py
+++ b/chrome/common/extensions/docs/build/directory.py
@@ -749,10 +749,12 @@ class Sample(dict):
     return has_b_popup or has_p_popup
 
   def is_hosted_app(self):
-    """ Returns true if the manifest has an app but not a local_path."""
+    """ Returns true if the manifest has an app but not a local_path (that's a
+    packaged app) nor a background (that's a platform app)."""
     return (self._manifest.has_key('app') and
             (not self._manifest['app'].has_key('launch') or
-             not self._manifest['app']['launch'].has_key('local_path')))
+             not self._manifest['app']['launch'].has_key('local_path')) and
+            not self._manifest['app'].has_key('background'))
 
   def is_packaged_app(self):
     """ Returns true if the manifest has an app/launch/local_path section."""