new file mode 100644
--- /dev/null
+++ b/b2g/dev/app.mozbuild
@@ -0,0 +1,25 @@
+# vim: set filetype=python:
+# 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/.
+
+if not CONFIG['LIBXUL_SDK']:
+    app_libxul_dirs = []
+    app_libxul_static_dirs = []
+    include('/toolkit/toolkit.mozbuild')
+
+if CONFIG['MOZ_EXTENSIONS']:
+    add_tier_dir('app', 'extensions')
+
+add_tier_dir('app', [CONFIG['MOZ_BRANDING_DIRECTORY']])
+
+if CONFIG['MOZ_WEBAPP_RUNTIME']:
+    add_tier_dir('app', 'webapprt')
+
+add_tier_dir('app', 'b2g/chrome')
+add_tier_dir('app', 'b2g/components')
+
+# Never add tier dirs after browser because they apparently won't get
+# packaged properly on Mac.
+add_tier_dir('app', 'browser')
+

new file mode 100644
--- /dev/null
+++ b/b2g/dev/build.mk
@@ -0,0 +1,6 @@
+# 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/.
+
+include $(topsrcdir)/browser/build.mk
+

new file mode 100644
--- /dev/null
+++ b/b2g/dev/confvars.sh
@@ -0,0 +1,9 @@
+#! /bin/sh
+# 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/.
+
+MOZ_B2G=1
+MOZ_MULET=1
+
+. ${srcdir}/browser/confvars.sh

--- a/browser/app/Makefile.in
+++ b/browser/app/Makefile.in
@@ -2,16 +2,19 @@
 # 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/.
 
 dist_dest   = $(DIST)/$(MOZ_MACBUNDLE_NAME)
 
 PREF_JS_EXPORTS = $(srcdir)/profile/firefox.js \
 		  $(NULL)
 
+ifdef MOZ_MULET
+PREF_JS_EXPORTS += $(topsrcdir)/b2g/app/b2g.js
+endif
 
 # hardcode en-US for the moment
 AB_CD = en-US
 
 DEFINES += \
   -DAB_CD=$(AB_CD) \
   -DFIREFOX_ICO='"$(DIST)/branding/firefox.ico"' \
   -DDOCUMENT_ICO='"$(DIST)/branding/document.ico"' \

--- a/browser/components/BrowserComponents.manifest
+++ b/browser/components/BrowserComponents.manifest
@@ -37,9 +37,11 @@ category command-line-validator b-browse
 #
 # In theory we should do this for all these instructions, but in practice it is
 # sufficient to do it for the app-startup one, and the file is simpler that way.
 
 component {eab9012e-5f74-4cbc-b2b5-a590235513cc} nsBrowserGlue.js
 contract @mozilla.org/browser/browserglue;1 {eab9012e-5f74-4cbc-b2b5-a590235513cc}
 category app-startup nsBrowserGlue service,@mozilla.org/browser/browserglue;1 application={3c2e2abc-06d4-11e1-ac3b-374f68613e61} application={ec8030f7-c20a-464f-9b0e-13a3a9e97384} application={aa3c5121-dab2-40e2-81ca-7ea25febc110} application={a23983c0-fd0e-11dc-95ff-0800200c9a66}
 component {d8903bf6-68d5-4e97-bcd1-e4d3012f721a} nsBrowserGlue.js
+#ifndef MOZ_MULET
 contract @mozilla.org/content-permission/prompt;1 {d8903bf6-68d5-4e97-bcd1-e4d3012f721a}
+#endif

--- a/configure.in
+++ b/configure.in
@@ -4197,22 +4197,27 @@ browser)
   ;;
 
 xulrunner)
   AC_DEFINE(MOZ_XULRUNNER)
   ;;
 b2g)
   AC_DEFINE(MOZ_B2G)
   ;;
+b2g/dev)
+  AC_DEFINE(MOZ_B2G)
+  AC_DEFINE(MOZ_MULET)
+  ;;
 esac
 
 AC_SUBST(MOZ_BUILD_APP)
 AC_SUBST(MOZ_PHOENIX)
 AC_SUBST(MOZ_XULRUNNER)
 AC_SUBST(MOZ_B2G)
+AC_SUBST(MOZ_MULET)
 AC_SUBST(MOZ_B2G_VERSION)
 
 AC_DEFINE_UNQUOTED(MOZ_BUILD_APP,$MOZ_BUILD_APP)
 
 dnl ========================================================
 dnl Check android sdk version depending on mobile target
 dnl ========================================================