Adding missing break in media_file_utility.cc.

There has been no reports of problems, but adding this to get it correct.

Review URL: https://webrtc-codereview.appspot.com/19599004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6322 4adac7df-926f-26a2-2b94-8c16560cd09d

webrtc/modules/media_file/source/media_file_utility.cc

@@ -2521,6 +2521,7 @@ int32_t ModuleFileUtility::FileDurationMs(const char* fileName,
                 break;
             }
 #endif
+            break;
         }
         case kFileFormatPreencodedFile:
         {