Refactored TTS extension code so that the platform-specific TTS...

chrome/browser/extensions/extension_tts_api.h

 // Copyright (c) 2010 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.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_EXTENSION_TTS_API_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_TTS_API_H_
 
 #include "chrome/browser/extensions/extension_function.h"
 #include "chrome/browser/extensions/extension_tts_api_util.h"
 
+// Abstract class that defines the native platform TTS interface.
+class ExtensionTtsPlatformImpl {
+ public:
+  static ExtensionTtsPlatformImpl* GetInstance();
+
+  // Speak the given utterance with the given parameters if possible,
+  // and return true on success. Utterance will always be nonempty.
+  // If the user does not specify the other values, language and gender
+  // will be empty strings, and rate, pitch, and volume will be -1.0.
+  virtual bool Speak(
+      const std::string& utterance,
+      const std::string& language,
+      const std::string& gender,
+      double rate,
+      double pitch,
+      double volume) = 0;
+
+  // Stop speaking immediately and return true on success.
+  virtual bool StopSpeaking() = 0;
+
+  // Return true if the synthesis engine is currently speaking.
+  virtual bool IsSpeaking() = 0;
+
+  virtual std::string error() { return error_; }
+  virtual void clear_error() { error_ = std::string(); }
+  virtual void set_error(const std::string& error) { error_ = error; }
+
+ protected:
+  ExtensionTtsPlatformImpl() {}
+  virtual ~ExtensionTtsPlatformImpl() {}
+
+  std::string error_;
+
+  DISALLOW_COPY_AND_ASSIGN(ExtensionTtsPlatformImpl);
+};
+
+//
+// Extension API function definitions
+//
+
 class ExtensionTtsSpeakFunction : public SyncExtensionFunction {
   ~ExtensionTtsSpeakFunction() {}
   virtual bool RunImpl();
   DECLARE_EXTENSION_FUNCTION_NAME("experimental.tts.speak")
 };
 
 class ExtensionTtsStopSpeakingFunction : public SyncExtensionFunction {
   ~ExtensionTtsStopSpeakingFunction() {}
   virtual bool RunImpl();
   DECLARE_EXTENSION_FUNCTION_NAME("experimental.tts.stop")
 };
 
 class ExtensionTtsIsSpeakingFunction : public SyncExtensionFunction {
   ~ExtensionTtsIsSpeakingFunction() {}
   virtual bool RunImpl();
   DECLARE_EXTENSION_FUNCTION_NAME("experimental.tts.isSpeaking")
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_TTS_API_H_