Proguard中混淆Volley jar包的问题

Question

最近项目里需要proguard混淆，其中对volley的混淆如下：

# volley
-keep class com.android.volley.** {*;}
-keep class com.android.volley.toolbox.** {*;}
-keep class com.android.volley.Response$* {*;}
-keep class com.android.volley.Request$* {*;}
-keep class com.android.volley.RequestQueue$* {*;}
-keep class com.android.volley.toolbox.HurlStack$* {*;}
-keep class com.android.volley.toolbox.ImageLoader$* {*;}
-keep class org.apache.http.** {*;}

但是运行时还是报错：

11-23 13:13:42.915 11269-11285/com.test.app E/AndroidRuntime: FATAL EXCEPTION: Thread-653
                                                                    Process: com.test.app, PID: 11269
                                                                    java.lang.NoClassDefFoundError: Failed resolution of: Lorg/apache/http/c/BasicStatusLine;
                                                                        at com.android.volley.toolbox.HurlStack.performRequest()
                                                                        at com.android.volley.toolbox.BasicNetwork.performRequest()
                                                                        at com.android.volley.NetworkDispatcher.run()
                                                                     Caused by: java.lang.ClassNotFoundException: Didn't find class "org.apache.http.c.BasicStatusLine" on path: DexPathList[[zip file "/system/app/test/test.apk"],nativeLibraryDirectories=[/system/app/test/lib/arm, /vendor/lib, /system/lib]]
                                                                        at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:56)
                                                                        at java.lang.ClassLoader.loadClass(ClassLoader.java:511)
                                                                        at java.lang.ClassLoader.loadClass(ClassLoader.java:469)
                                                                        at com.android.volley.toolbox.HurlStack.performRequest() 
                                                                        at com.android.volley.toolbox.BasicNetwork.performRequest() 
                                                                        at com.android.volley.NetworkDispatcher.run() 
                                                                        Suppressed: java.lang.ClassNotFoundException: org.apache.http.c.BasicStatusLine
                                                                        at java.lang.Class.classForName(Native Method)
                                                                        at java.lang.BootClassLoader.findClass(ClassLoader.java:781)
                                                                        at java.lang.BootClassLoader.loadClass(ClassLoader.java:841)
                                                                        at java.lang.ClassLoader.loadClass(ClassLoader.java:504)
                                                                                ... 4 more
                                                                     Caused by: java.lang.NoClassDefFoundError: Class not found using the boot class loader; no stack trace available

通过对proguard之后的apk进行反编译，发现volley包里的HurlStack类中import文件被混淆了，导致找不到class。这块谁能给出好的解释和解决方案？

补充：这个问题目前我已经解决，发现是在AndroidM系统中编译应用，由于AndroidM去除了org.apache.http的大部分类，导致我无法keep住org.apache.http的类。因为我加了一个org.apache.http.legacy.jar解决问题。但是具体原理还不是特别清楚，希望有专业人士能指导一下。