3 files changed, 67 insertions, 5 deletions
diff --git a/app/l10n_util.cc b/app/l10n_util.cc
index 375f3b6..d86f082 100644
--- a/app/l10n_util.cc
+++ b/app/l10n_util.cc
@@ -8,7 +8,9 @@
 #include <glib/gutils.h>
 #endif
 
+#include <algorithm>
 #include <cstdlib>
+#include <iterator>
 
 #include "app/app_paths.h"
 #include "app/l10n_util_collator.h"
@@ -30,6 +32,8 @@
 
 #if defined(OS_MACOSX)
 #include "app/l10n_util_mac.h"
+#elif defined(OS_WIN)
+#include "app/l10n_util_win.h"
 #endif
 
 namespace {
@@ -325,6 +329,10 @@ void AdjustParagraphDirectionality(string16* paragraph) {
 #endif
 }
 
+std::string GetCanonicalLocale(const std::string& locale) {
+  return base::i18n::GetCanonicalLocale(locale.c_str());
+}
+
 }  // namespace
 
 namespace l10n_util {
@@ -369,8 +377,16 @@ std::string GetApplicationLocale(const std::string& pref_locale) {
   if (!pref_locale.empty())
     candidates.push_back(pref_locale);
 
-  // Next, try the system locale.
-  candidates.push_back(base::i18n::GetConfiguredLocale());
+  // Next, try the overridden locale.
+  const std::vector<std::string>& languages = l10n_util::GetLocaleOverrides();
+  if (!languages.empty()) {
+    candidates.reserve(candidates.size() + languages.size());
+    std::transform(languages.begin(), languages.end(),
+                   std::back_inserter(candidates), &GetCanonicalLocale);
+  } else {
+    // If no override was set, defer to ICU
+    candidates.push_back(base::i18n::GetConfiguredLocale());
+  }
 
 #elif defined(OS_CHROMEOS)
 
diff --git a/app/l10n_util_win.cc b/app/l10n_util_win.cc
index 2f1f627..eacdb35 100644
--- a/app/l10n_util_win.cc
+++ b/app/l10n_util_win.cc
@@ -2,14 +2,17 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "app/l10n_util.h"
+#include "app/l10n_util_win.h"
 
-#include <algorithm>
 #include <windowsx.h>
+#include <algorithm>
+#include <iterator>
 
-#include "app/l10n_util_win.h"
+#include "app/l10n_util.h"
 #include "base/i18n/rtl.h"
+#include "base/lazy_instance.h"
 #include "base/string_number_conversions.h"
+#include "base/win/i18n.h"
 #include "base/win/windows_version.h"
 #include "grit/app_locale_settings.h"
 
@@ -52,6 +55,21 @@ bool IsFontPresent(const wchar_t* font_name) {
   return wcscmp(font_name, actual_font_name) == 0;
 }
 
+class OverrideLocaleHolder {
+ public:
+  OverrideLocaleHolder() {}
+  const std::vector<std::string>& value() const { return value_; }
+  void swap_value(std::vector<std::string>* override_value) {
+    value_.swap(*override_value);
+  }
+ private:
+  std::vector<std::string> value_;
+  DISALLOW_COPY_AND_ASSIGN(OverrideLocaleHolder);
+};
+
+base::LazyInstance<OverrideLocaleHolder>
+    override_locale_holder(base::LINKER_INITIALIZED);
+
 }  // namespace
 
 namespace l10n_util {
@@ -147,4 +165,21 @@ void AdjustUIFontForWindow(HWND hwnd) {
   }
 }
 
+void OverrideLocaleWithUILanguageList() {
+  std::vector<std::wstring> ui_languages;
+  if (base::win::i18n::GetThreadPreferredUILanguageList(&ui_languages)) {
+    std::vector<std::string> ascii_languages;
+    ascii_languages.reserve(ui_languages.size());
+    std::transform(ui_languages.begin(), ui_languages.end(),
+                   std::back_inserter(ascii_languages), &WideToASCII);
+    override_locale_holder.Get().swap_value(&ascii_languages);
+  } else {
+    NOTREACHED() << "Failed to determine the UI language for locale override.";
+  }
+}
+
+const std::vector<std::string>& GetLocaleOverrides() {
+  return override_locale_holder.Get().value();
+}
+
 }  // namespace l10n_util
diff --git a/app/l10n_util_win.h b/app/l10n_util_win.h
index 99a9df3..7a1dda5 100644
--- a/app/l10n_util_win.h
+++ b/app/l10n_util_win.h
@@ -7,6 +7,8 @@
 #pragma once
 
 #include <windows.h>
+#include <string>
+#include <vector>
 
 namespace l10n_util {
 
@@ -47,6 +49,15 @@ void AdjustUIFont(LOGFONT* logfont);
 // stored in the per-locale resource.
 void AdjustUIFontForWindow(HWND hwnd);
 
+// Allow processes to override the configured locale with the user's Windows UI
+// languages.  This function should generally be called once early in
+// Application startup.
+void OverrideLocaleWithUILanguageList();
+
+// Retrieve the locale override, or an empty vector if the locale has not been
+// or failed to be overridden.
+const std::vector<std::string>& GetLocaleOverrides();
+
 }  // namespace l10n_util
 
 #endif  // APP_L10N_UTIL_WIN_H_