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

chrome/browser/extensions/extension_tts_api.h

Index: chrome/browser/extensions/extension_tts_api.h
===================================================================
--- chrome/browser/extensions/extension_tts_api.h	(revision 62145)
+++ chrome/browser/extensions/extension_tts_api.h	(working copy)
@@ -8,6 +8,46 @@
 #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();