--- a/config/autoconf.mk.in
+++ b/config/autoconf.mk.in
@@ -77,16 +77,17 @@ MOZ_FS_LAYOUT = @MOZ_FS_LAYOUT@
 L10NBASEDIR     = @L10NBASEDIR@
 
 LIBXUL_DIST	= @LIBXUL_DIST@
 SYSTEM_LIBXUL   = @SYSTEM_LIBXUL@
 
 XULRUNNER_STUB_NAME = @XULRUNNER_STUB_NAME@
 
 MOZ_CHROME_FILE_FORMAT	= @MOZ_CHROME_FILE_FORMAT@
+MOZ_OMNIJAR             = @MOZ_OMNIJAR@
 
 MOZ_WIDGET_TOOLKIT	= @MOZ_WIDGET_TOOLKIT@
 MOZ_DFB			= @MOZ_DFB@
 MOZ_X11			= @MOZ_X11@
 
 MOZ_JS_LIBS		   = @MOZ_JS_LIBS@
 
 MOZ_DEBUG	= @MOZ_DEBUG@

--- a/configure.in
+++ b/configure.in
@@ -6109,30 +6109,44 @@ MOZ_ARG_ENABLE_BOOL(xterm-updates,
 [  --enable-xterm-updates  Update XTERM titles with current command.],
     MOZ_UPDATE_XTERM=1,
     MOZ_UPDATE_XTERM= )
 
 dnl =========================================================
 dnl = Chrome format
 dnl =========================================================
 MOZ_ARG_ENABLE_STRING([chrome-format],
-[  --enable-chrome-format=jar|flat|both|symlink
+[  --enable-chrome-format=jar|flat|both|symlink|omni
                           Select FORMAT of chrome files (default=jar)],
     MOZ_CHROME_FILE_FORMAT=`echo $enableval | tr A-Z a-z`)
 
-if test -z "$MOZ_CHROME_FILE_FORMAT"; then
-    MOZ_CHROME_FILE_FORMAT=jar
-fi
-
 if test "$MOZ_CHROME_FILE_FORMAT" != "jar" && 
     test "$MOZ_CHROME_FILE_FORMAT" != "flat" &&
     test "$MOZ_CHROME_FILE_FORMAT" != "symlink" &&
-    test "$MOZ_CHROME_FILE_FORMAT" != "both"; then
-    AC_MSG_ERROR([--enable-chrome-format must be set to either jar, flat, both, or symlink])
-fi
+    test "$MOZ_CHROME_FILE_FORMAT" != "both" &&
+    test "$MOZ_CHROME_FILE_FORMAT" != "omni"; then
+    AC_MSG_ERROR([--enable-chrome-format must be set to either jar, flat, both, symlink or omni])
+fi
+
+dnl =========================================================
+dnl Omnijar packaging (bug 552121)
+dnl =========================================================
+dnl Omnijar packaging is compatible with flat packaging.
+dnl In unpackaged builds, omnijar looks for files as if
+dnl things were flat packaged. After packaging, all files
+dnl are loaded from a single jar. MOZ_CHROME_FILE_FORMAT
+dnl is set to flat since putting files into jars is only
+dnl done during packaging with omnijar.
+if test "$MOZ_CHROME_FILE_FORMAT" = "omni"; then
+    MOZ_OMNIJAR=1
+    AC_DEFINE(MOZ_OMNIJAR)
+    MOZ_CHROME_FILE_FORMAT=flat
+fi
+
+AC_SUBST(MOZ_OMNIJAR)
 
 dnl ========================================================
 dnl = Define default location for MOZILLA_FIVE_HOME
 dnl ========================================================
 MOZ_ARG_WITH_STRING(default-mozilla-five-home,
 [  --with-default-mozilla-five-home
                           Set the default value for MOZILLA_FIVE_HOME],
 [ val=`echo $withval`
@@ -6526,16 +6540,20 @@ fi
 if test -n "$MOZ_ENABLE_LIBXUL" -a -n "$BUILD_STATIC_LIBS"; then
 	AC_MSG_ERROR([--enable-libxul is not compatible with --enable-static])
 fi
 
 if test -n "$MOZ_IPC" -a -z "$MOZ_ENABLE_LIBXUL"; then
     AC_MSG_ERROR([--enable-ipc requires --enable-libxul])
 fi
 
+if test -z "$MOZ_ENABLE_LIBXUL" -a -n "$MOZ_OMNIJAR"; then
+    AC_MSG_ERROR([Omnijar packaging is incompatible with --disable-libxul. Please either --enable-libxul or --enable-chrome-format=jar|flat|symlink]);
+fi
+
 if test -n "$MOZ_ENABLE_LIBXUL"; then
     XPCOM_LIBS="$LIBXUL_LIBS"
     AC_DEFINE(MOZ_ENABLE_LIBXUL)
 else
     if test -n "$BUILD_STATIC_LIBS"; then
         AC_DEFINE(MOZ_STATIC_BUILD)
     fi
     XPCOM_LIBS="$DYNAMIC_XPCOM_LIBS"