Update the SODA config file path for Windows

This CL updates the speech recognition recognizer to be compatible with
Windows. Chromium uses std::wstring for file paths; however, wide
characters should not be passed across API boundaries, so they must
be converted to plain C-style characters before being passed into the
SODA DLL.

Bug: 1116563
Change-Id: I920a994706fe9212b8ed50ecd5c6371090509e9a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2357609Reviewed-by: Jan Wilken Dörrie <jdoerrie@chromium.org>
Commit-Queue: Evan Liu <evliu@google.com>
Cr-Commit-Position: refs/heads/master@{#798958}

chrome/services/speech/speech_recognition_recognizer_impl.cc

@@ -131,7 +131,7 @@ void SpeechRecognitionRecognizerImpl::SendAudioToSpeechRecognitionService(
       soda_client_->DidAudioPropertyChange(sample_rate, channel_count)) {
     // Initialize the SODA instance.
     auto api_key = google_apis::GetSodaAPIKey();
-    auto config_file_path = config_path_.value();
+    std::string config_file_path = config_path_.AsUTF8Unsafe();
     SodaConfig config;
     config.channel_count = channel_count;
     config.sample_rate = sample_rate;