Revert bug 1299919 due to a failure building with CPP in environemnt.

diff --git build/autoconf/toolchain.m4 build/autoconf/toolchain.m4
index 8353967a180c..c8503e5d63f5 100644
--- build/autoconf/toolchain.m4
+++ build/autoconf/toolchain.m4
@@ -2,14 +2,6 @@
 dnl License, v. 2.0. If a copy of the MPL was not distributed with this
 dnl file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
-dnl Several autoconf functions AC_REQUIRE AC_PROG_CPP/AC_PROG_CXXCPP,
-dnl meaning they are called even when we don't call them explicitly.
-dnl However, theses checks are not necessary and python configure sets
-dnl the corresponding variables already, so just skip those tests
-dnl entirely.
-define([AC_PROG_CPP],[])
-define([AC_PROG_CXXCPP],[])
-
 AC_DEFUN([MOZ_TOOL_VARIABLES],
 [
 GNU_AS=
diff --git build/moz.configure/toolchain.configure build/moz.configure/toolchain.configure
index c69b5d12daf4..bba62023c836 100644
--- build/moz.configure/toolchain.configure
+++ build/moz.configure/toolchain.configure
@@ -754,23 +754,6 @@
     valid_compiler.try_compile(check_msg='%s works' % what,
                                onerror=compiler_error)
 
-
-    # Set CPP/CXXCPP for both the build system and old-configure. We don't
-    # need to check this works for preprocessing, because we already relied
-    # on $CC -E/$CXX -E doing preprocessing work to validate the compiler
-    # in the first place.
-    if host_or_target == target:
-        pp_var = {
-            'C': 'CPP',
-            'C++': 'CXXCPP',
-        }[language]
-
-        preprocessor = depends_if(valid_compiler)(
-                lambda x: list(x.wrapper) + [x.compiler, '-E'] + list(x.flags))
-
-        set_config(pp_var, preprocessor)
-        add_old_configure_assignment(pp_var, preprocessor)
-
     return valid_compiler
 
 
diff --git dom/bindings/GenerateCSS2PropertiesWebIDL.py dom/bindings/GenerateCSS2PropertiesWebIDL.py
index 73e1541c13b0..58ec60c29b10 100644
--- dom/bindings/GenerateCSS2PropertiesWebIDL.py
+++ dom/bindings/GenerateCSS2PropertiesWebIDL.py
@@ -16,7 +16,7 @@
     return "  [%s] attribute DOMString %s;\n" % (", ".join(extendedAttrs),
                                                  propName)
 def generate(output, idlFilename, preprocessorHeader):
-    cpp = list(buildconfig.substs['CPP'])
+    cpp = shellutil.split(buildconfig.substs['CPP'])
     cpp += shellutil.split(buildconfig.substs['ACDEFINES'])
     cpp.append(preprocessorHeader)
     preprocessed = subprocess.check_output(cpp)
diff --git js/src/old-configure.in js/src/old-configure.in
index 79541bdeb986..1cb4204aeeb3 100644
--- js/src/old-configure.in
+++ js/src/old-configure.in
@@ -140,6 +140,9 @@
 
 MOZ_TOOL_VARIABLES
 
+AC_PROG_CPP
+AC_PROG_CXXCPP
+
 dnl Special win32 checks
 dnl ========================================================
 
diff --git layout/style/GenerateCSSPropsGenerated.py layout/style/GenerateCSSPropsGenerated.py
index 4dc2a253a811..5038e9afe726 100644
--- layout/style/GenerateCSSPropsGenerated.py
+++ layout/style/GenerateCSSPropsGenerated.py
@@ -10,7 +10,7 @@
 from mozbuild import shellutil
 
 def get_properties(preprocessorHeader):
-    cpp = list(buildconfig.substs['CPP'])
+    cpp = shellutil.split(buildconfig.substs['CPP'])
     cpp += shellutil.split(buildconfig.substs['ACDEFINES'])
     cpp.append(preprocessorHeader)
     preprocessed = subprocess.check_output(cpp)
diff --git old-configure.in old-configure.in
index 863235e13176..545e82f83d56 100644
--- old-configure.in
+++ old-configure.in
@@ -241,6 +241,9 @@
 
 MOZ_TOOL_VARIABLES
 
+AC_PROG_CPP
+AC_PROG_CXXCPP
+
 dnl ========================================================
 dnl Special win32 checks
 dnl ========================================================