Fix TTS code to be compatible with new extension API parameter serialization.

chrome/browser/speech/extension_api/tts_engine_extension_api.cc

Index: chrome/browser/speech/extension_api/tts_engine_extension_api.cc
diff --git a/chrome/browser/speech/extension_api/tts_engine_extension_api.cc b/chrome/browser/speech/extension_api/tts_engine_extension_api.cc
index 4e9465a238c4d210f3c1125dacc0301ab2fe6ebf..ffaf83d426b658b871897c8109a1189f8cc37a43 100644
--- a/chrome/browser/speech/extension_api/tts_engine_extension_api.cc
+++ b/chrome/browser/speech/extension_api/tts_engine_extension_api.cc
@@ -181,6 +181,8 @@ void ExtensionTtsEngineSpeak(Utterance* utterance,
     options->Remove(constants::kSrcIdKey, NULL);
   if (options->HasKey(constants::kIsFinalEventKey))
     options->Remove(constants::kIsFinalEventKey, NULL);
+  if (options->HasKey(constants::kOnEventKey))
+    options->Remove(constants::kOnEventKey, NULL);
 
   args.Set(1, options);
   args.Set(2, Value::CreateIntegerValue(utterance->id()));