Fix the speech rate and volume on Chrome OS; after switching the

chrome/browser/extensions/extension_tts_api_chromeos.cc

 // Copyright (c) 2011 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 "base/memory/singleton.h"
 #include "base/message_loop.h"
 #include "base/string_number_conversions.h"
 #include "base/task.h"
 #include "chrome/browser/chromeos/cros/cros_library.h"
 #include "chrome/browser/chromeos/cros/speech_synthesis_library.h"
@@ skipping 70 matching lines @@
   if (!lang.empty()) {
     AppendSpeakOption(
         chromeos::SpeechSynthesisLibrary::kSpeechPropertyLocale,
         lang,
         &options);
   }
 
   if (params.rate >= 0.0) {
     AppendSpeakOption(
         chromeos::SpeechSynthesisLibrary::kSpeechPropertyRate,
-        DoubleToString(1.5 + params.rate * 2.5),
+        DoubleToString(params.rate),
         &options);
   }
 
   if (params.pitch >= 0.0) {
     // The TTS service allows a range of 0 to 2 for speech pitch.
     AppendSpeakOption(
         chromeos::SpeechSynthesisLibrary::kSpeechPropertyPitch,
         DoubleToString(params.pitch),
         &options);
   }
 
   if (params.volume >= 0.0) {
-    // The TTS service allows a range of 0 to 5 for speech volume.
+    // The Chrome OS TTS service allows a range of 0 to 5 for speech volume,
+    // but 5 clips, so map to a range of 0...4.
     AppendSpeakOption(
         chromeos::SpeechSynthesisLibrary::kSpeechPropertyVolume,
-        DoubleToString(params.volume * 5),
+        DoubleToString(params.volume * 4),
         &options);
   }
 
   if (!options.empty()) {
     cros_library->GetSpeechSynthesisLibrary()->SetSpeakProperties(
         options.c_str());
   }
 
   bool result =
       cros_library->GetSpeechSynthesisLibrary()->Speak(utterance.c_str());
@@ skipping 61 matching lines @@
       chromeos::SpeechSynthesisLibrary::kSpeechPropertyEquals +
       value +
       chromeos::SpeechSynthesisLibrary::kSpeechPropertyDelimiter;
 }
 
 // static
 ExtensionTtsPlatformImplChromeOs*
 ExtensionTtsPlatformImplChromeOs::GetInstance() {
   return Singleton<ExtensionTtsPlatformImplChromeOs>::get();
 }