Bug 1027651: Fix comment for XRE_UPDATE_ROOT_DIR. r=rstrong

xpcom/build/nsXULAppAPI.h

@@ -132,12 +132,32 @@
 #define XRE_ADDON_APP_DIR "XREAddonAppDir"
 
 /**
- * A directory service key which provides the update directory.
- * At present this is supported only on Windows.
- * Windows: Documents and Settings\<User>\Local Settings\Application Data\
- *          <Vendor>\<Application>\<relative path to app dir from Program Files>
- * If appDir is not under the Program Files, directory service will fail.
- * Callers should fallback to appDir.
+ * A directory service key which provides the update directory. Callers should
+ * fall back to appDir.
+ * Windows:    If vendor name exists:
+ *             Documents and Settings\<User>\Local Settings\Application Data\
+ *             <vendor name>\updates\
+ *             <hash of the path to XRE_EXECUTABLE_FILE’s parent directory>
+ *
+ *             If vendor name doesn't exist, but product name exists:
+ *             Documents and Settings\<User>\Local Settings\Application Data\
+ *             <product name>\updates\
+ *             <hash of the path to XRE_EXECUTABLE_FILE’s parent directory>
+ *
+ *             If neither vendor nor product name exists:
+ *               If app dir is under Program Files:
+ *               Documents and Settings\<User>\Local Settings\Application Data\
+ *               <relative path to app dir from Program Files>
+ *
+ *               If app dir isn’t under Program Files:
+ *               Documents and Settings\<User>\Local Settings\Application Data\
+ *               <MOZ_APP_NAME>
+ *
+ * Mac:        ~/Library/Caches/Mozilla/updates/<absolute path to app dir>
+ *
+ * Gonk:       /data/local
+ *
+ * All others: Parent directory of XRE_EXECUTABLE_FILE.
  */
 #define XRE_UPDATE_ROOT_DIR "UpdRootD"