--- a/config/Makefile.in
+++ b/config/Makefile.in
@@ -36,16 +36,17 @@ ifdef WRAP_SYSTEM_INCLUDES
 export-preqs = \
   $(call mkdir_deps,system_wrappers) \
   $(NULL)
 
 export:: $(export-preqs)
 	$(PYTHON) -m mozbuild.action.preprocessor $(DEFINES) $(ACDEFINES) \
 		-DMOZ_TREE_CAIRO=$(MOZ_TREE_CAIRO) \
 		-DMOZ_TREE_PIXMAN=$(MOZ_TREE_PIXMAN) \
+		-DMOZ_SYSTEM_HARFBUZZ=$(MOZ_SYSTEM_HARFBUZZ) \
 		-DMOZ_SYSTEM_HUNSPELL=$(MOZ_SYSTEM_HUNSPELL) \
 		-DMOZ_SYSTEM_BZ2=$(MOZ_SYSTEM_BZ2) \
 		-DMOZ_SYSTEM_ZLIB=$(MOZ_SYSTEM_ZLIB) \
 		-DMOZ_SYSTEM_PNG=$(MOZ_SYSTEM_PNG) \
 		-DMOZ_SYSTEM_JPEG=$(MOZ_SYSTEM_JPEG) \
 		-DMOZ_SYSTEM_LIBEVENT=$(MOZ_SYSTEM_LIBEVENT) \
 		-DMOZ_SYSTEM_LIBVPX=$(MOZ_SYSTEM_LIBVPX) \
 		-DMOZ_SYSTEM_ICU=$(MOZ_SYSTEM_ICU) \

--- a/config/system-headers
+++ b/config/system-headers
@@ -1263,16 +1263,21 @@ zlib.h
 #ifdef MOZ_ENABLE_STARTUP_NOTIFICATION
 libsn/sn.h
 libsn/sn-common.h
 libsn/sn-launchee.h
 libsn/sn-launcher.h
 libsn/sn-monitor.h
 libsn/sn-util.h
 #endif
+#if MOZ_SYSTEM_HARFBUZZ==1
+harfbuzz/hb-glib.h
+harfbuzz/hb-ot.h
+harfbuzz/hb.h
+#endif
 #if MOZ_SYSTEM_HUNSPELL==1
 hunspell.hxx
 #endif
 #if MOZ_SYSTEM_BZ2==1
 bzlib.h
 #endif
 #ifdef MOZ_ENABLE_GIO
 gio/gio.h

--- a/dom/base/moz.build
+++ b/dom/base/moz.build
@@ -476,16 +476,19 @@ include('/ipc/chromium/chromium-config.m
 FINAL_LIBRARY = 'xul'
 
 if CONFIG['MOZ_BUILD_APP'] in ['browser', 'mobile/android', 'xulrunner']:
     DEFINES['HAVE_SIDEBAR'] = True
 
 if CONFIG['MOZ_X11']:
     CXXFLAGS += CONFIG['TK_CFLAGS']
 
+if CONFIG['MOZ_SYSTEM_HARFBUZZ']:
+    CXXFLAGS += CONFIG['MOZ_HARFBUZZ_CFLAGS']
+
 GENERATED_FILES += [
     'PropertyUseCounterMap.inc',
     'UseCounterList.h',
 ]
 
 countermap = GENERATED_FILES['PropertyUseCounterMap.inc']
 countermap.script = 'gen-usecounters.py:property_map'
 countermap.inputs = ['UseCounters.conf']

--- a/gfx/harfbuzz/README-mozilla
+++ b/gfx/harfbuzz/README-mozilla
@@ -14,8 +14,13 @@ this file when updating harfbuzz, and ch
 
 The normal approach to updating harfbuzz, therefore, is to pull the latest HB
 source into a scratch directory and do a local build; then copy the original
 sources AND the generated header mentioned above from the build directory into
 the mozilla tree.
 
 If the collection of source files changes, manual updates to moz.build may be
 needed, as we don't use the upstream makefiles.
+
+The in-tree copy may be omitted during build by --with-system-harfbuzz.
+Make sure to keep pkg-config version check within toolkit/moz.configure in sync
+with checkout version or increment latest tag by one if it's not based
+on upstream release.

--- a/gfx/moz.build
+++ b/gfx/moz.build
@@ -5,26 +5,28 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 with Files('**'):
     BUG_COMPONENT = ('Core', 'Graphics')
 
 if CONFIG['MOZ_TREE_CAIRO']:
     DIRS += ['cairo']
 
+if not CONFIG['MOZ_SYSTEM_HARFBUZZ']:
+    DIRS += ['harfbuzz/src']
+
 DIRS += [
     '2d',
     'ycbcr',
     'angle',
     'src',
     'qcms',
     'gl',
     'layers',
     'graphite2/src',
-    'harfbuzz/src',
     'ots/src',
     'thebes',
     'ipc',
     'vr',
     'config',
     'webrender_bindings',
 ]
 

--- a/gfx/skia/generate_mozbuild.py
+++ b/gfx/skia/generate_mozbuild.py
@@ -138,16 +138,19 @@ if CONFIG['GNU_CXX'] and not CONFIG['CLA
 if CONFIG['CLANG_CXX'] or CONFIG['CLANG_CL']:
     CXXFLAGS += [
         '-Wno-implicit-fallthrough',
         '-Wno-inconsistent-missing-override',
         '-Wno-macro-redefined',
         '-Wno-unused-private-field',
     ]
 
+if CONFIG['MOZ_SYSTEM_HARFBUZZ']:
+    CXXFLAGS += CONFIG['MOZ_HARFBUZZ_CFLAGS']
+
 if CONFIG['MOZ_WIDGET_TOOLKIT'] in ('gtk2', 'gtk3', 'android'):
     CXXFLAGS += CONFIG['MOZ_CAIRO_CFLAGS']
     CXXFLAGS += CONFIG['CAIRO_FT_CFLAGS']
 
 if CONFIG['MOZ_WIDGET_TOOLKIT'] in ('gtk2', 'gtk3'):
     CXXFLAGS += CONFIG['MOZ_PANGO_CFLAGS']
 
 if CONFIG['MOZ_ENABLE_SKIA_PDF_SFNTLY']:

--- a/gfx/skia/moz.build
+++ b/gfx/skia/moz.build
@@ -748,16 +748,19 @@ if CONFIG['GNU_CXX'] and not CONFIG['CLA
 if CONFIG['CLANG_CXX'] or CONFIG['CLANG_CL']:
     CXXFLAGS += [
         '-Wno-implicit-fallthrough',
         '-Wno-inconsistent-missing-override',
         '-Wno-macro-redefined',
         '-Wno-unused-private-field',
     ]
 
+if CONFIG['MOZ_SYSTEM_HARFBUZZ']:
+    CXXFLAGS += CONFIG['MOZ_HARFBUZZ_CFLAGS']
+
 if CONFIG['MOZ_WIDGET_TOOLKIT'] in ('gtk2', 'gtk3', 'android'):
     CXXFLAGS += CONFIG['MOZ_CAIRO_CFLAGS']
     CXXFLAGS += CONFIG['CAIRO_FT_CFLAGS']
 
 if CONFIG['MOZ_WIDGET_TOOLKIT'] in ('gtk2', 'gtk3'):
     CXXFLAGS += CONFIG['MOZ_PANGO_CFLAGS']
 
 if CONFIG['MOZ_ENABLE_SKIA_PDF_SFNTLY']:

--- a/gfx/thebes/moz.build
+++ b/gfx/thebes/moz.build
@@ -270,11 +270,14 @@ if CONFIG['MOZ_WIDGET_TOOLKIT'] in ('and
 
 if CONFIG['MOZ_WIDGET_TOOLKIT'] in ('gtk2', 'gtk3'):
     CXXFLAGS += CONFIG['MOZ_PANGO_CFLAGS']
 
 LOCAL_INCLUDES += CONFIG['SKIA_INCLUDES']
 
 DEFINES['GRAPHITE2_STATIC'] = True
 
+if CONFIG['MOZ_SYSTEM_HARFBUZZ']:
+    CXXFLAGS += CONFIG['MOZ_HARFBUZZ_CFLAGS']
+
 if CONFIG['CLANG_CXX']:
     # Suppress warnings from Skia header files.
     SOURCES['gfxPlatform.cpp'].flags += ['-Wno-implicit-fallthrough']

--- a/intl/unicharutil/util/moz.build
+++ b/intl/unicharutil/util/moz.build
@@ -24,9 +24,12 @@ UNIFIED_SOURCES += [
     'nsUnicodeProperties.cpp',
 ]
 
 if CONFIG['ENABLE_INTL_API']:
     UNIFIED_SOURCES += [
         'ICUUtils.cpp',
     ]
 
+if CONFIG['MOZ_SYSTEM_HARFBUZZ']:
+    CXXFLAGS += CONFIG['MOZ_HARFBUZZ_CFLAGS']
+
 FINAL_LIBRARY = 'xul'

--- a/netwerk/dns/moz.build
+++ b/netwerk/dns/moz.build
@@ -64,16 +64,19 @@ etld_data = GENERATED_FILES['etld_data.i
 etld_data.script = 'prepare_tlds.py'
 etld_data.inputs = ['effective_tld_names.dat']
 
 # need to include etld_data.inc
 LOCAL_INCLUDES += [
     '/netwerk/base',
 ]
 
+if CONFIG['MOZ_SYSTEM_HARFBUZZ']:
+    CXXFLAGS += CONFIG['MOZ_HARFBUZZ_CFLAGS']
+
 if CONFIG['ENABLE_INTL_API']:
     DEFINES['IDNA2008'] = True
     USE_LIBS += ['icu']
 else:
     UNIFIED_SOURCES += [
         'nameprep.c',
     ]
 

--- a/toolkit/library/moz.build
+++ b/toolkit/library/moz.build
@@ -223,16 +223,19 @@ if CONFIG['SERVO_TARGET_DIR']:
         OS_LIBS += ['-L%s' % CONFIG['SERVO_TARGET_DIR'], '-lgeckoservo']
 
 if CONFIG['MOZ_SYSTEM_JPEG']:
     OS_LIBS += CONFIG['MOZ_JPEG_LIBS']
 
 if CONFIG['MOZ_SYSTEM_PNG']:
     OS_LIBS += CONFIG['MOZ_PNG_LIBS']
 
+if CONFIG['MOZ_SYSTEM_HARFBUZZ']:
+    OS_LIBS += CONFIG['MOZ_HARFBUZZ_LIBS']
+
 if CONFIG['MOZ_SYSTEM_HUNSPELL']:
     OS_LIBS += CONFIG['MOZ_HUNSPELL_LIBS']
 
 if CONFIG['MOZ_SYSTEM_LIBEVENT']:
     OS_LIBS += CONFIG['MOZ_LIBEVENT_LIBS']
 
 if CONFIG['MOZ_SYSTEM_LIBVPX']:
     OS_LIBS += CONFIG['MOZ_LIBVPX_LIBS']

--- a/toolkit/moz.configure
+++ b/toolkit/moz.configure
@@ -338,16 +338,26 @@ def ft2_info(freetype2_combined_info, tr
         return freetype2_combined_info
 
 set_config('FT2_LIBS', delayed_getattr(ft2_info, 'libs'))
 add_old_configure_assignment('FT2_LIBS',
                              delayed_getattr(ft2_info, 'libs'))
 add_old_configure_assignment('FT2_CFLAGS',
                              delayed_getattr(ft2_info, 'cflags'))
 
+# HarfBuzz
+# ==============================================================
+option('--with-system-harfbuzz',
+       help="Use system harfbuzz (located with pkgconfig)")
+
+system_harfbuzz = pkg_check_modules('MOZ_HARFBUZZ', 'harfbuzz >= 1.4.2',
+                                    when='--with-system-harfbuzz')
+
+set_config('MOZ_SYSTEM_HARFBUZZ', depends_if(system_harfbuzz)(lambda _: True))
+
 # Apple platform decoder support
 # ==============================================================
 @depends(toolkit)
 def applemedia(toolkit):
     if toolkit in ('cocoa', 'uikit'):
         return True
 
 set_config('MOZ_APPLEMEDIA', applemedia)