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

earcon_manager.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 <stdio.h>
 #include <stdlib.h>
 
 #include "base/scoped_ptr.h"
 #include "earcon_manager.h"
 #include "log.h"
@@ skipping 189 matching lines @@
       delete[] old_audio_data;
       frames += new_frames;
     }
 
     pos += chunk_bytes + 8;
   }
 
   if (frames && channels && rate) {
     return LoadEarcon(frames, audio_data.get(), channels, rate, loop);
   }
+  return -1;
 }
 
 void EarconManager::Play(int earcon_id) {
   earcons_[earcon_id].is_playing = true;
   earcons_[earcon_id].position = 0;
 }
 
 void EarconManager::Stop(int earcon_id) {
   earcons_[earcon_id].is_playing = false;
 }
@@ skipping 36 matching lines @@
       data[j] = value;
     }
 
     earcons_[i].position += count;
     if (earcons_[i].position == earcons_[i].frame_count)
       earcons_[i].is_playing = false;
   }
 }
 
 }  // namespace speech_synthesis