Improve speech contextual announcements and startCallback synchronization

chrome/browser/chromeos/accessibility/speech_monitor.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/chromeos/accessibility/speech_monitor.h"
 
 namespace chromeos {
 
 namespace {
 const char kChromeVoxEnabledMessage[] = "chrome vox spoken feedback is ready";
@@ skipping 66 matching lines @@
   voice.name = "SpeechMonitor";
   voice.events.insert(TTS_EVENT_END);
 }
 
 std::string SpeechMonitor::error() {
   return "";
 }
 
 void SpeechMonitor::WillSpeakUtteranceWithVoice(const Utterance* utterance,
                                                 const VoiceData& voice_data) {
+  // Filter out empty utterances which can be used to trigger a start event from
+  // tts as an earcon sync.
+  if (utterance->text() == "")
+    return;
+
   VLOG(0) << "Speaking " << utterance->text();
   utterance_queue_.push_back(utterance->text());
   if (loop_runner_.get())
     loop_runner_->Quit();
 }
 
 }  // namespace chromeos