--- a/aclocal.m4
+++ b/aclocal.m4
@@ -11,16 +11,17 @@ builtin(include, mozilla/build/autoconf/
 builtin(include, mozilla/build/autoconf/pkg.m4)dnl
 builtin(include, mozilla/build/autoconf/codeset.m4)dnl
 builtin(include, mozilla/build/autoconf/altoptions.m4)dnl
 builtin(include, mozilla/build/autoconf/mozprog.m4)dnl
 builtin(include, mozilla/build/autoconf/acwinpaths.m4)dnl
 builtin(include, mozilla/build/autoconf/lto.m4)dnl
 builtin(include, mozilla/build/autoconf/frameptr.m4)dnl
 builtin(include, mozilla/build/autoconf/compiler-opts.m4)dnl
+builtin(include, mozilla/build/autoconf/zlib.m4)dnl
 
 MOZ_PROG_CHECKMSYS()
 
 # Read the user's .mozconfig script.  We can't do this in
 # configure.in: autoconf puts the argument parsing code above anything
 # expanded from configure.in, and we need to get the configure options
 # from .mozconfig in place before that argument parsing code.
 MOZ_READ_MOZCONFIG(mozilla)

--- a/configure.in
+++ b/configure.in
@@ -58,17 +58,16 @@ dnl ====================================
 _SUBDIR_HOST_CXXFLAGS="$HOST_CXXFLAGS"
 _SUBDIR_HOST_LDFLAGS="$HOST_LDFLAGS"
 _SUBDIR_CONFIG_ARGS="$ac_configure_args"
 
 dnl Set the version number of the libs included with mozilla
 dnl ========================================================
 MOZJPEG=62
 MOZPNG=10401
-MOZZLIB=0x1230
 NSPR_VERSION=4
 NSS_VERSION=3
 
 dnl Set the minimum version of toolkit libs used by mozilla
 dnl ========================================================
 GLIB_VERSION=1.2.0
 PERL_VERSION=5.006
 PYTHON_VERSION=2.5
@@ -863,18 +862,16 @@ LIB_SUFFIX=a
 ASM_SUFFIX=s
 IMPORT_LIB_SUFFIX=
 TARGET_MD_ARCH=unix
 DIRENT_INO=d_ino
 MOZ_USER_DIR=".mozilla"
 
 MOZ_JPEG_CFLAGS=
 MOZ_JPEG_LIBS='$(call EXPAND_LIBNAME_PATH,mozjpeg,$(DEPTH)/mozilla/jpeg)'
-MOZ_ZLIB_CFLAGS=
-MOZ_ZLIB_LIBS='$(call EXPAND_LIBNAME_PATH,mozz,$(DEPTH)/mozilla/modules/zlib/src)'
 MOZ_BZ2_CFLAGS=
 MOZ_BZ2_LIBS='$(call EXPAND_LIBNAME_PATH,bz2,$(DEPTH)/mozilla/modules/libbz2/src)'
 MOZ_PNG_CFLAGS=
 MOZ_PNG_LIBS='$(call EXPAND_LIBNAME_PATH,mozpng,$(DEPTH)/mozilla/modules/libimg/png)'
 MOZ_JS_STATIC_LIBS='-L$(LIBXUL_DIST)/bin -ljs_static'
 MOZ_JS_SHARED_LIBS='-L$(LIBXUL_DIST)/bin -lmozjs'
 DYNAMIC_XPCOM_LIBS='-L$(LIBXUL_DIST)/bin -lxpcom -lxpcom_core -lmozalloc'
 MOZ_FIX_LINK_PATHS='-Wl,-rpath-link,$(LIBXUL_DIST)/bin:/usr/lib:/usr/local/lib:/lib -Wl,-rpath-link,$(prefix)/lib'
@@ -3947,57 +3944,29 @@ fi
 CFLAGS=$_SAVE_CFLAGS
 LDFLAGS=$_SAVE_LDFLAGS
 LIBS=$_SAVE_LIBS
 
 if test -n "${JPEG_DIR}" -a -d "${JPEG_DIR}" -a "$MOZ_NATIVE_JPEG" = 1; then
     MOZ_JPEG_CFLAGS="-I${JPEG_DIR}/include"
     MOZ_JPEG_LIBS="-L${JPEG_DIR}/lib ${MOZ_JPEG_LIBS}"
 fi
+fi # SKIP_LIBRARY_CHECKS
 
 dnl system ZLIB support
 dnl ========================================================
-MOZ_ARG_WITH_STRING(system-zlib,
-[  --with-system-zlib[=PFX]
-                          Use system libz [installed at prefix PFX]],
-    ZLIB_DIR=$withval)
-
-_SAVE_CFLAGS=$CFLAGS
-_SAVE_LDFLAGS=$LDFLAGS
-_SAVE_LIBS=$LIBS
-if test -n "${ZLIB_DIR}" -a "${ZLIB_DIR}" != "yes"; then
-    CFLAGS="-I${ZLIB_DIR}/include $CFLAGS"
-    LDFLAGS="-L${ZLIB_DIR}/lib $LDFLAGS"
-fi
-if test -z "$ZLIB_DIR" -o "$ZLIB_DIR" = no; then
-    MOZ_NATIVE_ZLIB=
-else
-    AC_CHECK_LIB(z, gzread, [MOZ_NATIVE_ZLIB=1 MOZ_ZLIB_LIBS="-lz"], 
-	  [MOZ_NATIVE_ZLIB=])
-fi
-if test "$MOZ_NATIVE_ZLIB" = 1; then
-    MOZZLIBNUM=`echo $MOZZLIB | awk -F. '{printf "0x%x\n", ((($1 * 16 + $2) * 16) + $3) * 16 + $4}'`
-    AC_TRY_COMPILE([ #include <stdio.h>
-                     #include <string.h>
-                     #include <zlib.h> ],
-                   [ #if ZLIB_VERNUM < $MOZZLIBNUM
-                     #error "Insufficient zlib version ($MOZZLIBNUM required)."
-                     #endif ],
-                   MOZ_NATIVE_ZLIB=1,
-AC_MSG_ERROR([Insufficient zlib version for --with-system-zlib ($MOZZLIB required)]))
-fi
-CFLAGS=$_SAVE_CFLAGS
-LDFLAGS=$_SAVE_LDFLAGS
-LIBS=$_SAVE_LIBS
-
-if test "${ZLIB_DIR}" -a -d "${ZLIB_DIR}" -a "$MOZ_NATIVE_ZLIB" = 1; then
-    MOZ_ZLIB_CFLAGS="-I${ZLIB_DIR}/include"
-    MOZ_ZLIB_LIBS="-L${ZLIB_DIR}/lib ${ZLIB_LIBS}"
-fi
-
+
+MOZ_ZLIB_CHECK([1.2.3])
+
+if test "$MOZ_NATIVE_ZLIB" != 1; then
+    MOZ_ZLIB_CFLAGS=
+    MOZ_ZLIB_LIBS='$(call EXPAND_LIBNAME_PATH,mozz,$(DEPTH)/mozilla/modules/zlib/src)'
+fi
+
+if test -z "$SKIP_LIBRARY_CHECKS"; then
 dnl system BZIP2 Support
 dnl ========================================================
 MOZ_ARG_WITH_STRING(system-bz2,
 [  --with-system-bz2[=PFX]
                           Use system libbz2 [installed at prefix PFX]],
     BZ2_DIR=$withval)
 
 _SAVE_CFLAGS=$CFLAGS
@@ -6546,23 +6515,20 @@ COMPILE_CXXFLAGS=`echo \
     $_DEFINES_CXXFLAGS \
 	$_DEPEND_CFLAGS \
     $COMPILE_CXXFLAGS`
 
 AC_SUBST(MOZ_NATIVE_MAKEDEPEND)
 AC_SUBST(SYSTEM_LIBXUL)
 AC_SUBST(MOZ_NATIVE_JPEG)
 AC_SUBST(MOZ_NATIVE_PNG)
-AC_SUBST(MOZ_NATIVE_ZLIB)
 AC_SUBST(MOZ_NATIVE_BZ2)
 
 AC_SUBST(MOZ_JPEG_CFLAGS)
 AC_SUBST(MOZ_JPEG_LIBS)
-AC_SUBST(MOZ_ZLIB_CFLAGS)
-AC_SUBST(MOZ_ZLIB_LIBS)
 AC_SUBST(MOZ_BZ2_CFLAGS)
 AC_SUBST(MOZ_BZ2_LIBS)
 AC_SUBST(MOZ_PNG_CFLAGS)
 AC_SUBST(MOZ_PNG_LIBS)
 
 AC_SUBST(NSPR_CFLAGS)
 AC_SUBST(NSPR_LIBS)
 AC_SUBST(MOZ_NATIVE_NSPR)