Add missed imports

Author: mrleolink

sample/src/main/java/com/nostra13/universalimageloader/sample/ext/OkHttpImageDownloader.java

@@ -16,9 +16,12 @@
 package com.nostra13.universalimageloader.sample.ext;
 
 import android.content.Context;
+
+import com.nostra13.universalimageloader.core.assist.ContentLengthInputStream;
 import com.nostra13.universalimageloader.core.download.BaseImageDownloader;
 import com.squareup.okhttp.OkHttpClient;
 import com.squareup.okhttp.Request;
+import com.squareup.okhttp.ResponseBody;
 
 import java.io.IOException;
 import java.io.InputStream;