--- a/gfx/thebes/gfxAndroidPlatform.cpp
+++ b/gfx/thebes/gfxAndroidPlatform.cpp
@@ -5,16 +5,17 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "base/basictypes.h"
 
 #include "gfxAndroidPlatform.h"
 #include "mozilla/gfx/2D.h"
 #include "mozilla/CountingAllocatorBase.h"
 #include "mozilla/intl/LocaleService.h"
+#include "mozilla/intl/OSPreferences.h"
 #include "mozilla/Preferences.h"
 
 #include "gfx2DGlue.h"
 #include "gfxFT2FontList.h"
 #include "gfxImageSurface.h"
 #include "gfxTextRun.h"
 #include "mozilla/dom/ContentChild.h"
 #include "nsXULAppAPI.h"
@@ -30,16 +31,17 @@
 #include FT_MODULE_H
 
 #include "GeneratedJNINatives.h"
 
 using namespace mozilla;
 using namespace mozilla::dom;
 using namespace mozilla::gfx;
 using mozilla::intl::LocaleService;
+using mozilla::intl::OSPreferences;
 
 static FT_Library gPlatformFTLibrary = nullptr;
 
 class FreetypeReporter final : public nsIMemoryReporter,
                                public CountingAllocatorBase<FreetypeReporter>
 {
 private:
     ~FreetypeReporter() {}
@@ -134,16 +136,23 @@ IsJapaneseLocale()
         sInitialized = true;
 
         nsAutoCString appLocale;
         LocaleService::GetInstance()->GetAppLocaleAsLangTag(appLocale);
 
         const nsDependentCSubstring lang(appLocale, 0, 2);
         if (lang.EqualsLiteral("ja")) {
             sIsJapanese = true;
+        } else {
+            OSPreferences::GetInstance()->GetSystemLocale(appLocale);
+
+            const nsDependentCSubstring lang(appLocale, 0, 2);
+            if (lang.EqualsLiteral("ja")) {
+                sIsJapanese = true;
+            }
         }
     }
 
     return sIsJapanese;
 }
 
 void
 gfxAndroidPlatform::GetCommonFallbackFonts(uint32_t aCh, uint32_t aNextCh,

--- a/gfx/thebes/gfxPlatformFontList.cpp
+++ b/gfx/thebes/gfxPlatformFontList.cpp
@@ -1,15 +1,16 @@
 /* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 4 -*-
  * 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 "mozilla/Logging.h"
 #include "mozilla/intl/LocaleService.h"
+#include "mozilla/intl/OSPreferences.h"
 
 #include "gfxPlatformFontList.h"
 #include "gfxTextRun.h"
 #include "gfxUserFontSet.h"
 
 #include "nsCRT.h"
 #include "nsGkAtoms.h"
 #include "nsServiceManagerUtils.h"
@@ -24,16 +25,17 @@
 #include "mozilla/Telemetry.h"
 #include "mozilla/TimeStamp.h"
 #include "mozilla/gfx/2D.h"
 
 #include <locale.h>
 
 using namespace mozilla;
 using mozilla::intl::LocaleService;
+using mozilla::intl::OSPreferences;
 
 #define LOG_FONTLIST(args) MOZ_LOG(gfxPlatform::GetLog(eGfxLog_fontlist), \
                                LogLevel::Debug, args)
 #define LOG_FONTLIST_ENABLED() MOZ_LOG_TEST( \
                                    gfxPlatform::GetLog(eGfxLog_fontlist), \
                                    LogLevel::Debug)
 #define LOG_FONTINIT(args) MOZ_LOG(gfxPlatform::GetLog(eGfxLog_fontinit), \
                                LogLevel::Debug, args)
@@ -1086,33 +1088,57 @@ gfxPlatformFontList::AppendCJKPrefLangs(
                         break;
                     default:
                         break;
                 }
                 p++;
             }
         }
 
+        // Try using app's locale
         nsAutoCString localeStr;
         LocaleService::GetInstance()->GetAppLocaleAsLangTag(localeStr);
 
-        const nsACString& lang = Substring(localeStr, 0, 2);
-        if (lang.EqualsLiteral("ja")) {
-            AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_Japanese);
-        } else if (lang.EqualsLiteral("zh")) {
-            const nsACString& region = Substring(localeStr, 3, 2);
-            if (region.EqualsLiteral("CN")) {
-                AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_ChineseCN);
-            } else if (region.EqualsLiteral("TW")) {
-                AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_ChineseTW);
-            } else if (region.EqualsLiteral("HK")) {
-                AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_ChineseHK);
-            }
-        } else if (lang.EqualsLiteral("ko")) {
-            AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_Korean);
+        {
+          const nsACString& lang = Substring(localeStr, 0, 2);
+          if (lang.EqualsLiteral("ja")) {
+              AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_Japanese);
+          } else if (lang.EqualsLiteral("zh")) {
+              const nsACString& region = Substring(localeStr, 3, 2);
+              if (region.EqualsLiteral("CN")) {
+                  AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_ChineseCN);
+              } else if (region.EqualsLiteral("TW")) {
+                  AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_ChineseTW);
+              } else if (region.EqualsLiteral("HK")) {
+                  AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_ChineseHK);
+              }
+          } else if (lang.EqualsLiteral("ko")) {
+              AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_Korean);
+          }
+        }
+
+        // Then test OS locale
+        OSPreferences::GetInstance()->GetSystemLocale(localeStr);
+
+        {
+          const nsACString& lang = Substring(localeStr, 0, 2);
+          if (lang.EqualsLiteral("ja")) {
+              AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_Japanese);
+          } else if (lang.EqualsLiteral("zh")) {
+              const nsACString& region = Substring(localeStr, 3, 2);
+              if (region.EqualsLiteral("CN")) {
+                  AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_ChineseCN);
+              } else if (region.EqualsLiteral("TW")) {
+                  AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_ChineseTW);
+              } else if (region.EqualsLiteral("HK")) {
+                  AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_ChineseHK);
+              }
+          } else if (lang.EqualsLiteral("ko")) {
+              AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_Korean);
+          }
         }
 
         // last resort... (the order is same as old gfx.)
         AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_Japanese);
         AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_Korean);
         AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_ChineseCN);
         AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_ChineseHK);
         AppendPrefLang(tempPrefLangs, tempLen, eFontPrefLang_ChineseTW);