Provide script/gypi support for manifest generation

extensions/common/file_util.h

Index: extensions/common/file_util.h
diff --git a/extensions/common/file_util.h b/extensions/common/file_util.h
index 32c370ee96bdbb9ed15a31896920bd02812ac2e1..fbf77b299b4f6a71950fa92d12484a4e0171e39d 100644
--- a/extensions/common/file_util.h
+++ b/extensions/common/file_util.h
@@ -61,6 +61,12 @@ scoped_refptr<Extension> LoadExtension(const base::FilePath& extension_root,
 base::DictionaryValue* LoadManifest(const base::FilePath& extension_root,
                                     std::string* error);
 
+// Convenience overload for specifying a manifest filename.
+base::DictionaryValue* LoadManifest(
+    const base::FilePath& extension_root,
+    const base::FilePath::CharType* manifest_filename,
+    std::string* error);
+
 // Returns true if the given extension object is valid and consistent.
 // May also append a series of warning messages to |warnings|, but they
 // should not prevent the extension from running.