Code: void ExtensionTtsController::OnSpeechFinished(
    int request_id, const std::string& error_message) {
  if (!current_utterance_ || request_id != current_utterance_->id())
    return;
  current_utterance_->set_error(error_message);
  FinishCurrentUtterance();
  SpeakNextUtterance();
}

Commit Message: Extend TTS extension API to support richer events returned from the engine
to the client. Previously we just had a completed event; this adds start,
word boundary, sentence boundary, and marker boundary. In addition,
interrupted and canceled, which were previously errors, now become events.
Mac and Windows implementations extended to support as many of these events
as possible.

BUG=67713
BUG=70198
BUG=75106
BUG=83404

TEST=Updates all TTS API tests to be event-based, and adds new tests.
Review URL: http://codereview.chromium.org/6792014

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@91665 0039d316-1c4b-4281-b951-d872f2087c98
CWE ID: CWE-20
void ExtensionTtsController::OnSpeechFinished(
