Use "en_all" hotword model for dsp device with locales "en_*".

This change updates the logic for setting DSP model based on different locales.
See the linked bug for more details.

Bug: b/134125220
Test: local compile and manually test.
Change-Id: If4f33cf038f373853e8a9ff3b0fa1b3885320d8c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1648832
Commit-Queue: Meilin Wang <meilinw@chromium.org>
Reviewed-by: Xiaohui Chen <xiaohuic@chromium.org>
Cr-Commit-Position: refs/heads/master@{#681415}

chromeos/services/assistant/platform/audio_input_impl.cc

@@ -8,6 +8,7 @@
 #include "base/logging.h"
 #include "base/metrics/histogram_functions.h"
 #include "base/stl_util.h"
+#include "base/strings/string_util.h"
 #include "base/timer/timer.h"
 #include "chromeos/audio/cras_audio_handler.h"
 #include "chromeos/dbus/power/power_manager_client.h"
@@ -388,6 +389,13 @@ void AudioInputImpl::SetDspHotwordLocale(std::string pref_locale) {
     std::string region_code = pref_locale;
     pref_locale.append("_").append(region_code);
   }
+
+  // For locales with language code "en", use "en_all" hotword model.
+  std::vector<std::string> code_strings = base::SplitString(
+      pref_locale, "_", base::TRIM_WHITESPACE, base::SPLIT_WANT_ALL);
+  if (code_strings.size() > 0 && code_strings[0] == "en")
+    pref_locale = "en_all";
+
   uint64_t dsp_node_id;
   base::StringToUint64(hotword_device_id_, &dsp_node_id);
   chromeos::CrasAudioHandler::Get()->SetHotwordModel(