Create a Manifest to get attributes instead of peeking in the Dictionary a manifest is based on.

BUG=181074,180296

Review URL: https://chromiumcodereview.appspot.com/12391050

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@187220 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/chrome/common/extensions/extension.h b/chrome/common/extensions/extension.h
index 3ecb571..5e1b917 100644
--- a/chrome/common/extensions/extension.h
+++ b/chrome/common/extensions/extension.h
@@ -494,9 +494,7 @@
   }
 
   // App-related.
-  bool is_app() const {
-    return is_legacy_packaged_app() || is_hosted_app() || is_platform_app();
-  }
+  bool is_app() const;
   bool is_platform_app() const;
   bool is_hosted_app() const;
   bool is_legacy_packaged_app() const;