--- a/b2g/config/mozconfigs/common
+++ b/b2g/config/mozconfigs/common
@@ -1,7 +1,7 @@
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
-# This file is included by all b2g mozconfigs
+# This file is included at the top of all b2g mozconfigs
 
 . "$topsrcdir/build/mozconfig.common"

new file mode 100644
--- /dev/null
+++ b/b2g/config/mozconfigs/common.override
@@ -0,0 +1,7 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# This file is included at the bottom of all b2g mozconfigs
+
+. "$topsrcdir/build/mozconfig.common.override"

--- a/b2g/config/mozconfigs/gb_armv7a_gecko/debug
+++ b/b2g/config/mozconfigs/gb_armv7a_gecko/debug
@@ -12,8 +12,10 @@ ac_add_options --with-gonk-toolchain-pre
 ac_add_options --disable-elf-hack
 ac_add_options --enable-debug-symbols
 ac_add_options --enable-debug
 ac_add_options --with-ccache
 ENABLE_MARIONETTE=1
 
 # Enable dump() from JS.
 export CXXFLAGS=-DMOZ_ENABLE_JS_DUMP
+
+. "$topsrcdir/b2g/config/mozconfigs/common.override"

--- a/b2g/config/mozconfigs/gb_armv7a_gecko/nightly
+++ b/b2g/config/mozconfigs/gb_armv7a_gecko/nightly
@@ -12,8 +12,10 @@ ac_add_options --with-gonk-toolchain-pre
 ac_add_options --disable-elf-hack
 ac_add_options --enable-debug-symbols
 ac_add_options --enable-profiling
 ac_add_options --with-ccache
 ENABLE_MARIONETTE=1
 
 # Enable dump() from JS.
 export CXXFLAGS=-DMOZ_ENABLE_JS_DUMP
+
+. "$topsrcdir/b2g/config/mozconfigs/common.override"

--- a/b2g/config/mozconfigs/ics_armv7a_gecko/debug
+++ b/b2g/config/mozconfigs/ics_armv7a_gecko/debug
@@ -13,8 +13,10 @@ ac_add_options --with-gonk-toolchain-pre
 ac_add_options --disable-elf-hack
 ac_add_options --enable-debug-symbols
 ac_add_options --enable-debug
 #ac_add_options --with-ccache
 ENABLE_MARIONETTE=1
 
 # Enable dump() from JS.
 export CXXFLAGS="-DMOZ_ENABLE_JS_DUMP -include $topsrcdir/gonk-toolchain/gonk-misc/Unicode.h -include $topsrcdir/gonk-toolchain/system/vold/ResponseCode.h"
+
+. "$topsrcdir/b2g/config/mozconfigs/common.override"

--- a/b2g/config/mozconfigs/ics_armv7a_gecko/nightly
+++ b/b2g/config/mozconfigs/ics_armv7a_gecko/nightly
@@ -15,8 +15,10 @@ ac_add_options --with-gonk-toolchain-pre
 ac_add_options --disable-elf-hack
 ac_add_options --enable-debug-symbols
 ac_add_options --enable-profiling
 #ac_add_options --with-ccache
 ENABLE_MARIONETTE=1
 
 # Enable dump() from JS.
 export CXXFLAGS="-DMOZ_ENABLE_JS_DUMP -include $topsrcdir/gonk-toolchain/gonk-misc/Unicode.h -include $topsrcdir/gonk-toolchain/system/vold/ResponseCode.h"
+
+. "$topsrcdir/b2g/config/mozconfigs/common.override"

--- a/b2g/config/mozconfigs/linux32_gecko/nightly
+++ b/b2g/config/mozconfigs/linux32_gecko/nightly
@@ -33,8 +33,10 @@ mk_add_options MOZ_MAKE_FLAGS="-j4"
 # Use ccache
 ac_add_options --with-ccache=/usr/bin/ccache
 
 #B2G options
 ac_add_options --enable-application=b2g
 ENABLE_MARIONETTE=1
 ac_add_options --disable-elf-hack
 export CXXFLAGS=-DMOZ_ENABLE_JS_DUMP
+
+. "$topsrcdir/b2g/config/mozconfigs/common.override"

--- a/b2g/config/mozconfigs/linux64_gecko/nightly
+++ b/b2g/config/mozconfigs/linux64_gecko/nightly
@@ -33,8 +33,10 @@ mk_add_options MOZ_MAKE_FLAGS="-j4"
 # Use ccache
 ac_add_options --with-ccache=/usr/bin/ccache
 
 #B2G options
 ac_add_options --enable-application=b2g
 ENABLE_MARIONETTE=1
 ac_add_options --disable-elf-hack
 export CXXFLAGS=-DMOZ_ENABLE_JS_DUMP
+
+. "$topsrcdir/b2g/config/mozconfigs/common.override"

--- a/b2g/config/mozconfigs/macosx64_gecko/nightly
+++ b/b2g/config/mozconfigs/macosx64_gecko/nightly
@@ -21,8 +21,10 @@ ac_add_options --enable-warnings-as-erro
 
 # B2G Stuff
 ac_add_options --enable-application=b2g
 ac_add_options --enable-debug-symbols
 ac_add_options --with-ccache
 ENABLE_MARIONETTE=1
 
 export CXXFLAGS=-DMOZ_ENABLE_JS_DUMP
+
+. "$topsrcdir/b2g/config/mozconfigs/common.override"

--- a/b2g/config/mozconfigs/win32_gecko/nightly
+++ b/b2g/config/mozconfigs/win32_gecko/nightly
@@ -24,8 +24,10 @@ else
   . $topsrcdir/build/win32/mozconfig.vs2010
 fi
 
 # B2G Options
 ac_add_options --enable-application=b2g
 ENABLE_MARIONETTE=1
 
 export CXXFLAGS=-DMOZ_ENABLE_JS_DUMP
+
+. "$topsrcdir/b2g/config/mozconfigs/common.override"

--- a/browser/config/mozconfigs/linux32/debug
+++ b/browser/config/mozconfigs/linux32/debug
@@ -17,8 +17,10 @@ mk_add_options MOZ_MAKE_FLAGS="-j4"
 #Use ccache
 ac_add_options --with-ccache=/usr/bin/ccache
 
 # Treat warnings as errors in directories with FAIL_ON_WARNINGS.
 ac_add_options --enable-warnings-as-errors
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
+
+. "$topsrcdir/build/mozconfig.common.override"

--- a/browser/config/mozconfigs/linux32/debug-asan
+++ b/browser/config/mozconfigs/linux32/debug-asan
@@ -11,8 +11,10 @@ ac_add_options --enable-valgrind
 # Avoid dependency on libstdc++ 4.5
 ac_add_options --enable-stdcxx-compat
 
 # Enable parallel compiling
 mk_add_options MOZ_MAKE_FLAGS="-j4"
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
+
+. "$topsrcdir/build/mozconfig.common.override"

--- a/browser/config/mozconfigs/linux32/l10n-mozconfig
+++ b/browser/config/mozconfigs/linux32/l10n-mozconfig
@@ -1,7 +1,9 @@
 ac_add_options --with-l10n-base=../../l10n-central
 ac_add_options --enable-official-branding
 ac_add_options --enable-update-channel=${MOZ_UPDATE_CHANNEL}
 ac_add_options --enable-update-packaging
 
 . $topsrcdir/build/unix/mozconfig.linux
 
+
+. "$topsrcdir/build/mozconfig.common.override"

--- a/browser/config/mozconfigs/linux32/nightly
+++ b/browser/config/mozconfigs/linux32/nightly
@@ -31,8 +31,10 @@ ac_add_options --enable-warnings-as-erro
 # Enable parallel compiling
 mk_add_options MOZ_MAKE_FLAGS="-j4"
 
 # Use ccache
 ac_add_options --with-ccache=/usr/bin/ccache
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
+
+. "$topsrcdir/build/mozconfig.common.override"

--- a/browser/config/mozconfigs/linux32/nightly-asan
+++ b/browser/config/mozconfigs/linux32/nightly-asan
@@ -13,8 +13,10 @@ ac_add_options --enable-codesighs
 # Avoid dependency on libstdc++ 4.5
 ac_add_options --enable-stdcxx-compat
 
 # Enable parallel compiling
 mk_add_options MOZ_MAKE_FLAGS="-j4"
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
+
+. "$topsrcdir/build/mozconfig.common.override"

--- a/browser/config/mozconfigs/linux32/qt
+++ b/browser/config/mozconfigs/linux32/qt
@@ -21,8 +21,10 @@ ac_add_options --with-ccache=/usr/bin/cc
 # QT Options
 export PKG_CONFIG_PATH=/tools/qt-4.6.3/qt/lib/pkgconfig
 ac_add_options --with-qtdir=/tools/qt-4.6.3/qt
 ac_add_options --enable-default-toolkit=cairo-qt
 ac_add_options --disable-crashreporter
 
 # Treat warnings as errors in directories with FAIL_ON_WARNINGS.
 ac_add_options --enable-warnings-as-errors
+
+. "$topsrcdir/build/mozconfig.common.override"

--- a/browser/config/mozconfigs/linux32/release
+++ b/browser/config/mozconfigs/linux32/release
@@ -19,8 +19,10 @@ export MOZ_TELEMETRY_REPORTING=1
 # Treat warnings as errors in directories with FAIL_ON_WARNINGS.
 ac_add_options --enable-warnings-as-errors
 
 # Enable parallel compiling
 mk_add_options MOZ_MAKE_FLAGS="-j4"
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
+
+. "$topsrcdir/build/mozconfig.common.override"

--- a/browser/config/mozconfigs/linux32/rpm
+++ b/browser/config/mozconfigs/linux32/rpm
@@ -24,8 +24,10 @@ mk_add_options PROFILE_GEN_SCRIPT='$(PYT
 # Enable parallel compiling
 mk_add_options MOZ_MAKE_FLAGS="-j4"
 
 #Use ccache
 ac_add_options --with-ccache=/usr/bin/ccache
 
 # Treat warnings as errors in directories with FAIL_ON_WARNINGS.
 ac_add_options --enable-warnings-as-errors
+
+. "$topsrcdir/build/mozconfig.common.override"

--- a/browser/config/mozconfigs/linux64/debug
+++ b/browser/config/mozconfigs/linux64/debug
@@ -17,8 +17,10 @@ mk_add_options MOZ_MAKE_FLAGS="-j4"
 # Use ccache
 ac_add_options --with-ccache=/usr/bin/ccache
 
 # Treat warnings as errors in directories with FAIL_ON_WARNINGS.
 ac_add_options --enable-warnings-as-errors
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
+
+. "$topsrcdir/build/mozconfig.common.override"

--- a/browser/config/mozconfigs/linux64/debug-asan
+++ b/browser/config/mozconfigs/linux64/debug-asan
@@ -11,8 +11,10 @@ ac_add_options --enable-valgrind
 # Avoid dependency on libstdc++ 4.5
 ac_add_options --enable-stdcxx-compat
 
 # Enable parallel compiling
 mk_add_options MOZ_MAKE_FLAGS="-j4"
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
+
+. "$topsrcdir/build/mozconfig.common.override"

--- a/browser/config/mozconfigs/linux64/l10n-mozconfig
+++ b/browser/config/mozconfigs/linux64/l10n-mozconfig
@@ -1,7 +1,9 @@
 ac_add_options --with-l10n-base=../../l10n-central
 ac_add_options --enable-official-branding
 ac_add_options --enable-update-channel=${MOZ_UPDATE_CHANNEL}
 ac_add_options --enable-update-packaging
 
 . $topsrcdir/build/unix/mozconfig.linux
 
+
+. "$topsrcdir/build/mozconfig.common.override"

--- a/browser/config/mozconfigs/linux64/nightly
+++ b/browser/config/mozconfigs/linux64/nightly
@@ -31,8 +31,10 @@ ac_add_options --enable-warnings-as-erro
 # Enable parallel compiling
 mk_add_options MOZ_MAKE_FLAGS="-j4"
 
 # Use ccache
 ac_add_options --with-ccache=/usr/bin/ccache
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
+
+. "$topsrcdir/build/mozconfig.common.override"

--- a/browser/config/mozconfigs/linux64/nightly-asan
+++ b/browser/config/mozconfigs/linux64/nightly-asan
@@ -13,8 +13,10 @@ ac_add_options --enable-codesighs
 # Avoid dependency on libstdc++ 4.5
 ac_add_options --enable-stdcxx-compat
 
 # Enable parallel compiling
 mk_add_options MOZ_MAKE_FLAGS="-j4"
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
+
+. "$topsrcdir/build/mozconfig.common.override"

--- a/browser/config/mozconfigs/linux64/release
+++ b/browser/config/mozconfigs/linux64/release
@@ -19,8 +19,10 @@ export MOZ_TELEMETRY_REPORTING=1
 # Treat warnings as errors in directories with FAIL_ON_WARNINGS.
 ac_add_options --enable-warnings-as-errors
 
 # Enable parallel compiling
 mk_add_options MOZ_MAKE_FLAGS="-j4"
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
+
+. "$topsrcdir/build/mozconfig.common.override"

--- a/browser/config/mozconfigs/linux64/rpm
+++ b/browser/config/mozconfigs/linux64/rpm
@@ -24,8 +24,10 @@ mk_add_options PROFILE_GEN_SCRIPT='$(PYT
 # Enable parallel compiling
 mk_add_options MOZ_MAKE_FLAGS="-j4"
 
 #Use ccache
 ac_add_options --with-ccache=/usr/bin/ccache
 
 # Treat warnings as errors in directories with FAIL_ON_WARNINGS.
 ac_add_options --enable-warnings-as-errors
+
+. "$topsrcdir/build/mozconfig.common.override"

--- a/browser/config/mozconfigs/macosx-universal/nightly
+++ b/browser/config/mozconfigs/macosx-universal/nightly
@@ -21,8 +21,10 @@ mk_add_options MOZ_MAKE_FLAGS="-j12"
 
 ac_add_options --with-macbundlename-prefix=Firefox
 
 # Treat warnings as errors in directories with FAIL_ON_WARNINGS.
 ac_add_options --enable-warnings-as-errors
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
+
+. "$topsrcdir/build/mozconfig.common.override"

--- a/browser/config/mozconfigs/macosx-universal/release
+++ b/browser/config/mozconfigs/macosx-universal/release
@@ -15,8 +15,10 @@ export MOZ_TELEMETRY_REPORTING=1
 # Treat warnings as errors in directories with FAIL_ON_WARNINGS.
 ac_add_options --enable-warnings-as-errors
 
 # Enable parallel compiling
 mk_add_options MOZ_MAKE_FLAGS="-j4"
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
+
+. "$topsrcdir/build/mozconfig.common.override"

--- a/browser/config/mozconfigs/macosx-universal/shark
+++ b/browser/config/mozconfigs/macosx-universal/shark
@@ -19,8 +19,10 @@ ac_add_options --enable-shark
 ac_add_options --enable-dtrace
 
 # Need this to prevent name conflicts with the normal nightly build packages
 export MOZ_PKG_SPECIAL="shark"
 
 # Treat warnings as errors in directories with FAIL_ON_WARNINGS.
 ac_add_options --enable-warnings-as-errors
 ac_add_options --with-ccache
+
+. "$topsrcdir/build/mozconfig.common.override"

--- a/browser/config/mozconfigs/macosx32/debug
+++ b/browser/config/mozconfigs/macosx32/debug
@@ -10,8 +10,10 @@ mk_add_options MOZ_MAKE_FLAGS="-j12"
 
 # Needed to enable breakpad in application.ini
 export MOZILLA_OFFICIAL=1
 
 ac_add_options --with-macbundlename-prefix=Firefox
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
+
+. "$topsrcdir/build/mozconfig.common.override"

--- a/browser/config/mozconfigs/macosx64/debug
+++ b/browser/config/mozconfigs/macosx64/debug
@@ -14,8 +14,10 @@ export MOZILLA_OFFICIAL=1
 
 ac_add_options --with-macbundlename-prefix=Firefox
 
 # Treat warnings as errors in directories with FAIL_ON_WARNINGS.
 ac_add_options --enable-warnings-as-errors
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
+
+. "$topsrcdir/build/mozconfig.common.override"

--- a/browser/config/mozconfigs/macosx64/debug-asan
+++ b/browser/config/mozconfigs/macosx64/debug-asan
@@ -7,8 +7,10 @@ ac_add_options --enable-accessibility
 
 # Enable parallel compiling
 mk_add_options MOZ_MAKE_FLAGS="-j12"
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
 
 ac_add_options --with-macbundlename-prefix=Firefox
+
+. "$topsrcdir/build/mozconfig.common.override"

--- a/browser/config/mozconfigs/macosx64/l10n-mozconfig
+++ b/browser/config/mozconfigs/macosx64/l10n-mozconfig
@@ -1,7 +1,9 @@
 . "$topsrcdir/browser/config/mozconfigs/common"
 
 ac_add_options --with-l10n-base=../../l10n-central
 ac_add_options --enable-official-branding
 ac_add_options --enable-update-channel=${MOZ_UPDATE_CHANNEL}
 ac_add_options --enable-update-packaging
 ac_add_options --with-ccache
+
+. "$topsrcdir/build/mozconfig.common.override"

--- a/browser/config/mozconfigs/win32/debug
+++ b/browser/config/mozconfigs/win32/debug
@@ -17,8 +17,10 @@ fi
 if test "$PROCESSOR_ARCHITECTURE" = "AMD64" -o "$PROCESSOR_ARCHITEW6432" = "AMD64"; then
   . $topsrcdir/build/win32/mozconfig.vs2010-win64
 else
   . $topsrcdir/build/win32/mozconfig.vs2010
 fi
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
+
+. "$topsrcdir/build/mozconfig.common.override"

--- a/browser/config/mozconfigs/win32/l10n-mozconfig
+++ b/browser/config/mozconfigs/win32/l10n-mozconfig
@@ -5,8 +5,10 @@ ac_add_options --enable-update-packaging
 ac_add_options --enable-official-branding
 ac_add_options --with-l10n-base=../../l10n-central
 
 if test "$PROCESSOR_ARCHITECTURE" = "AMD64" -o "$PROCESSOR_ARCHITEW6432" = "AMD64"; then
   . $topsrcdir/build/win32/mozconfig.vs2010-win64
 else
   . $topsrcdir/build/win32/mozconfig.vs2010
 fi
+
+. "$topsrcdir/build/mozconfig.common.override"

--- a/browser/config/mozconfigs/win32/nightly
+++ b/browser/config/mozconfigs/win32/nightly
@@ -26,8 +26,10 @@ fi
 if test "$PROCESSOR_ARCHITECTURE" = "AMD64" -o "$PROCESSOR_ARCHITEW6432" = "AMD64"; then
   . $topsrcdir/build/win32/mozconfig.vs2010-win64
 else
   . $topsrcdir/build/win32/mozconfig.vs2010
 fi
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
+
+. "$topsrcdir/build/mozconfig.common.override"

--- a/browser/config/mozconfigs/win32/release
+++ b/browser/config/mozconfigs/win32/release
@@ -23,8 +23,10 @@ fi
 if test "$PROCESSOR_ARCHITECTURE" = "AMD64" -o "$PROCESSOR_ARCHITEW6432" = "AMD64"; then
   . $topsrcdir/build/win32/mozconfig.vs2010-win64
 else
   . $topsrcdir/build/win32/mozconfig.vs2010
 fi
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
+
+. "$topsrcdir/build/mozconfig.common.override"

--- a/browser/config/mozconfigs/win64/debug
+++ b/browser/config/mozconfigs/win64/debug
@@ -10,8 +10,10 @@ ENABLE_MARIONETTE=1
 export MOZILLA_OFFICIAL=1
 
 mk_add_options MOZ_MAKE_FLAGS=-j1
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
 
 . $topsrcdir/build/win64/mozconfig.vs2010
+
+. "$topsrcdir/build/mozconfig.common.override"

--- a/browser/config/mozconfigs/win64/nightly
+++ b/browser/config/mozconfigs/win64/nightly
@@ -19,8 +19,10 @@ export MOZILLA_OFFICIAL=1
 export MOZ_TELEMETRY_REPORTING=1
 
 mk_add_options MOZ_MAKE_FLAGS=-j1
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
 
 . $topsrcdir/build/win64/mozconfig.vs2010
+
+. "$topsrcdir/build/mozconfig.common.override"

--- a/build/mozconfig.common
+++ b/build/mozconfig.common
@@ -1,9 +1,11 @@
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 # Common mozconfig for all users
 #
 # Add options to this file that will be inherited by all in-tree mozconfigs.
 # This is useful for eg try builds with nondefault options that apply to all
-# architectures.
+# architectures, though note that if you want to override options set in
+# another mozconfig file, you'll need to use mozconfig.common.override instead
+# of this file.

new file mode 100644
--- /dev/null
+++ b/build/mozconfig.common.override
@@ -0,0 +1,11 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# Common mozconfig for all users
+#
+# Add options to this file that will be inherited by all in-tree mozconfigs.
+# This file is included at the *end* of the mozconfigs, and so may be used
+# to override anything done previously.
+#
+# The common expected usage is for try builds with nondefault options.

--- a/mobile/android/config/mozconfigs/common
+++ b/mobile/android/config/mozconfigs/common
@@ -1,7 +1,7 @@
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
-# This file is included by all native android mozconfigs
+# This file is included at the top of all native android mozconfigs
 
 . "$topsrcdir/build/mozconfig.common"

new file mode 100644
--- /dev/null
+++ b/mobile/android/config/mozconfigs/common.override
@@ -0,0 +1,7 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# This file is included at the bottom of all native android mozconfigs
+
+. "$topsrcdir/build/mozconfig.common.override"

--- a/mobile/xul/config/mozconfigs/android/common
+++ b/mobile/xul/config/mozconfigs/android/common
@@ -1,1 +1,7 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# This file is included at the top of all Android XUL mozconfigs
+
 . "$topsrcdir/build/mozconfig.common"

new file mode 100644
--- /dev/null
+++ b/mobile/xul/config/mozconfigs/android/common.override
@@ -0,0 +1,7 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# This file is included at the bottom of all Android XUL mozconfigs
+
+. "$topsrcdir/build/mozconfig.common.override"

--- a/mobile/xul/config/mozconfigs/android/debug
+++ b/mobile/xul/config/mozconfigs/android/debug
@@ -17,8 +17,10 @@ ac_add_options --with-system-zlib
 export JAVA_HOME=/tools/jdk6
 export MOZILLA_OFFICIAL=1
 export MOZ_TELEMETRY_REPORTING=1
 
 ac_add_options --with-branding=mobile/xul/branding/nightly
 
 # Treat warnings as errors in directories with FAIL_ON_WARNINGS.
 ac_add_options --enable-warnings-as-errors
+
+. "$topsrcdir/mobile/xul/config/mozconfigs/android/common.override"

--- a/mobile/xul/config/mozconfigs/android/nightly
+++ b/mobile/xul/config/mozconfigs/android/nightly
@@ -20,8 +20,10 @@ ac_add_options --enable-update-channel=$
 export JAVA_HOME=/tools/jdk6
 export MOZILLA_OFFICIAL=1
 export MOZ_TELEMETRY_REPORTING=1
 
 ac_add_options --with-branding=mobile/xul/branding/nightly
 
 # Treat warnings as errors in directories with FAIL_ON_WARNINGS.
 ac_add_options --enable-warnings-as-errors
+
+. "$topsrcdir/mobile/xul/config/mozconfigs/android/common.override"

--- a/mobile/xul/config/mozconfigs/android/release
+++ b/mobile/xul/config/mozconfigs/android/release
@@ -16,8 +16,10 @@ ac_add_options --enable-updater
 ac_add_options --enable-update-channel=${MOZ_UPDATE_CHANNEL}
 
 export JAVA_HOME=/tools/jdk6
 export MOZILLA_OFFICIAL=1
 export MOZ_TELEMETRY_REPORTING=1
 
 ac_add_options --enable-official-branding
 ac_add_options --with-branding=mobile/xul/branding/beta
+
+. "$topsrcdir/mobile/xul/config/mozconfigs/android/common.override"

--- a/xulrunner/config/mozconfigs/common
+++ b/xulrunner/config/mozconfigs/common
@@ -1,1 +1,7 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# This file is included at the top of all xulrunner mozconfigs
+
 . "$topsrcdir/build/mozconfig.common"

new file mode 100644
--- /dev/null
+++ b/xulrunner/config/mozconfigs/common.override
@@ -0,0 +1,7 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# This file is included at the bottom of all xulrunner mozconfigs
+
+. "$topsrcdir/build/mozconfig.common.override"

--- a/xulrunner/config/mozconfigs/linux32/xulrunner
+++ b/xulrunner/config/mozconfigs/linux32/xulrunner
@@ -9,8 +9,10 @@ ac_add_options --disable-tests
 # Avoid dependency on libstdc++ 4.5
 ac_add_options --enable-stdcxx-compat
 
 # Enable parallel compiling
 mk_add_options MOZ_MAKE_FLAGS="-j4"
 
 #Use ccache
 ac_add_options --with-ccache=/usr/bin/ccache
+
+. "$topsrcdir/xulrunner/config/mozconfigs/common.override"

--- a/xulrunner/config/mozconfigs/linux32/xulrunner-qt
+++ b/xulrunner/config/mozconfigs/linux32/xulrunner-qt
@@ -15,8 +15,10 @@ mk_add_options MOZ_MAKE_FLAGS="-j4"
 #Use ccache
 ac_add_options --with-ccache=/usr/bin/ccache
 
 # QT Options
 export PKG_CONFIG_PATH=/tools/qt-4.6.3/qt/lib/pkgconfig
 ac_add_options --with-qtdir=/tools/qt-4.6.3/qt
 ac_add_options --enable-default-toolkit=cairo-qt
 ac_add_options --disable-crashreporter
+
+. "$topsrcdir/xulrunner/config/mozconfigs/common.override"

--- a/xulrunner/config/mozconfigs/linux64/xulrunner
+++ b/xulrunner/config/mozconfigs/linux64/xulrunner
@@ -9,8 +9,10 @@ ac_add_options --disable-tests
 # Avoid dependency on libstdc++ 4.5
 ac_add_options --enable-stdcxx-compat
 
 # Enable parallel compiling
 mk_add_options MOZ_MAKE_FLAGS="-j4"
 
 #Use ccache
 ac_add_options --with-ccache=/usr/bin/ccache
+
+. "$topsrcdir/xulrunner/config/mozconfigs/common.override"

--- a/xulrunner/config/mozconfigs/macosx-universal/xulrunner
+++ b/xulrunner/config/mozconfigs/macosx-universal/xulrunner
@@ -2,8 +2,10 @@
 
 export MOZILLA_OFFICIAL=1
 
 ac_add_options --enable-application=xulrunner
 ac_add_options --disable-tests
 
 # Enable parallel compiling
 mk_add_options MOZ_MAKE_FLAGS="-j4"
+
+. "$topsrcdir/xulrunner/config/mozconfigs/common.override"

--- a/xulrunner/config/mozconfigs/win32/xulrunner
+++ b/xulrunner/config/mozconfigs/win32/xulrunner
@@ -9,8 +9,10 @@ ac_add_options --disable-tests
 
 mk_add_options MOZ_MAKE_FLAGS=-j1
 
 if test "$PROCESSOR_ARCHITECTURE" = "AMD64" -o "$PROCESSOR_ARCHITEW6432" = "AMD64"; then
   . $topsrcdir/build/win32/mozconfig.vs2010-win64
 else
   . $topsrcdir/build/win32/mozconfig.vs2010
 fi
+
+. "$topsrcdir/xulrunner/config/mozconfigs/common.override"

--- a/xulrunner/config/mozconfigs/win64/xulrunner
+++ b/xulrunner/config/mozconfigs/win64/xulrunner
@@ -6,8 +6,10 @@ ac_add_options --host=x86_64-pc-mingw32
 export MOZILLA_OFFICIAL=1
 export JAVA_HOME=/d/jdk1.6.0_14
 
 ac_add_options --enable-application=xulrunner
 ac_add_options --enable-jemalloc
 ac_add_options --disable-tests
 
 mk_add_options MOZ_MAKE_FLAGS=-j1
+
+. "$topsrcdir/xulrunner/config/mozconfigs/common.override"