Enable -Wall -Werror and fix 2 compile-errors it would introduce.

speech_synthesizer_service.cc

 // Copyright (c) 2010 The Chromium OS 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 <iostream>
 #include <base/basictypes.h>
 #include <base/command_line.h>
 #include <chromeos/dbus/dbus.h>
 #include <chromeos/dbus/service_constants.h>
 #include <chromeos/glib/object.h>
@@ skipping 104 matching lines @@
 gboolean SpeechSynthesizerService::AddProperties(gchar *properties) {
   if (properties == NULL) {
     return false;
   }
   string props(properties);
   if (props.compare("") == 0) {
     return true;
   }
   string token = "";
   while(1) {
-    int sep = props.find(";");
+    unsigned int sep = props.find(";");
     if (sep == string::npos) {
       token = props;
     } else {
       token = props.substr(0, sep);
       props = props.substr(sep + 1);
     }
     if (token.empty() || token.compare("") == 0) {
       break;
     }
     int eq = token.find("=");
@@ skipping 58 matching lines @@
 
 gboolean SpeechSynthesizerService::IsSpeaking(
     gboolean* OUT_isSpeaking_requested,
     GError **error) {
   *OUT_isSpeaking_requested = (ttsService->GetStatus() == TTS_BUSY);
   return true;
 }
 
 } // namespace speech_synthesis