lacros: Pass locale to lacros on command line

The UX plan for UI language is to use a single shared locale for OS and
browser. See bug.

Pass the locale on the command line because Lacros needs it very early
in startup, before zygote fork.

This CL doesn't include the changes to browser WebUI settings. We'll
need to add a link-out to OS settings, similar to how Chrome OS
browser settings work today.

Bug: 1139618
Change-Id: I0202ed54d4c4a4956ecb31f04ecde670aea5595f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2600316
Commit-Queue: James Cook <jamescook@chromium.org>
Reviewed-by: Erik Chen <erikchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#838983}

chrome/browser/chrome_content_browser_client.cc

@@ -664,6 +664,7 @@
 #include "chrome/browser/chrome_browser_main_parts_lacros.h"
 #include "chrome/browser/ui/views/chrome_browser_main_extra_parts_views_lacros.h"
 #include "chromeos/lacros/lacros_chrome_service_impl.h"
+#include "ui/base/ui_base_switches.h"
 #endif
 
 #if BUILDFLAG(USE_MINIKIN_HYPHENATION) && !defined(OS_ANDROID)
@@ -2453,6 +2454,12 @@ void ChromeContentBrowserClient::AppendExtraCommandLineSwitches(
 
     command_line->CopySwitchesFrom(browser_command_line, kSwitchNames,
                                    base::size(kSwitchNames));
+#endif
+#if BUILDFLAG(IS_CHROMEOS_LACROS)
+    // Ensure zygote loads the resource bundle for the right locale.
+    static const char* const kMoreSwitchNames[] = {switches::kLang};
+    command_line->CopySwitchesFrom(browser_command_line, kMoreSwitchNames,
+                                   base::size(kMoreSwitchNames));
 #endif
   } else if (process_type == switches::kGpuProcess) {
     // If --ignore-gpu-blocklist is passed in, don't send in crash reports

chrome/browser/chromeos/crosapi/browser_manager.cc

@@ -30,6 +30,7 @@
 #include "base/system/sys_info.h"
 #include "base/task/task_traits.h"
 #include "base/task/thread_pool.h"
+#include "chrome/browser/browser_process.h"
 #include "chrome/browser/chromeos/crosapi/ash_chrome_service_impl.h"
 #include "chrome/browser/chromeos/crosapi/browser_loader.h"
 #include "chrome/browser/chromeos/crosapi/browser_util.h"
@@ -313,6 +314,10 @@ void BrowserManager::StartWithLogFile(base::ScopedFD logfd) {
   std::string crash_dir =
       browser_util::GetUserDataDir().Append("crash_dumps").AsUTF8Unsafe();
 
+  // Pass the locale via command line instead of via LacrosInitParams because
+  // the Lacros browser process needs it early in startup, before zygote fork.
+  std::string locale = g_browser_process->GetApplicationLocale();
+
   // Static configuration should be enabled from Lacros rather than Ash. This
   // vector should only be used for dynamic configuration.
   // TODO(https://crbug.com/1145713): Remove existing static configuration.
@@ -321,7 +326,7 @@ void BrowserManager::StartWithLogFile(base::ScopedFD logfd) {
                                    "--user-data-dir=" + user_data_dir,
                                    "--enable-gpu-rasterization",
                                    "--enable-oop-rasterization",
-                                   "--lang=en-US",
+                                   "--lang=" + locale,
                                    "--enable-crashpad",
                                    "--enable-webgl-image-chromium",
                                    "--breakpad-dump-location=" + crash_dir};