libbinder: remove unused ProcessState mRootDir

Bug: N/A
Test: N/A
Change-Id: I1cf4a886b61d9ecff93881a04b9d69dae88d8ee5
diff --git a/libs/binder/include/binder/ProcessState.h b/libs/binder/include/binder/ProcessState.h
index 2405ab6..ca29440 100644
--- a/libs/binder/include/binder/ProcessState.h
+++ b/libs/binder/include/binder/ProcessState.h
@@ -124,7 +124,6 @@
 
             Vector<handle_entry>mHandleToObject;
 
-            String8             mRootDir;
             bool                mThreadPoolStarted;
     volatile int32_t            mThreadPoolSeq;