Add mechanism for Parcel to not allow FDs to be written to it.

This is to help implement issue #5224703.

Change-Id: I026a5890495537d15b57fe61227a640aac806d46
diff --git a/include/binder/Parcel.h b/include/binder/Parcel.h
index bfe13f0..57f5dd2 100644
--- a/include/binder/Parcel.h
+++ b/include/binder/Parcel.h
@@ -46,7 +46,7 @@
     size_t              dataAvail() const;
     size_t              dataPosition() const;
     size_t              dataCapacity() const;
-    
+
     status_t            setDataSize(size_t size);
     void                setDataPosition(size_t pos) const;
     status_t            setDataCapacity(size_t size);
@@ -56,6 +56,8 @@
     status_t            appendFrom(const Parcel *parcel,
                                    size_t start, size_t len);
 
+    bool                setAllowFds(bool allowFds);
+
     bool                hasFileDescriptors() const;
 
     // Writes the RPC header.
@@ -212,6 +214,7 @@
 
     mutable bool        mFdsKnown;
     mutable bool        mHasFds;
+    bool                mAllowFds;
     
     release_func        mOwner;
     void*               mOwnerCookie;