Add |readString8| method which returns failure

Add a new method to return |String8| read failures from Parcels.

BUG: 30189542
Change-Id: I65b59887dd9a15068abe95d24d390aa577bc49a6
diff --git a/include/binder/Parcel.h b/include/binder/Parcel.h
index 97a3376..d6a9377 100644
--- a/include/binder/Parcel.h
+++ b/include/binder/Parcel.h
@@ -246,6 +246,7 @@
 
     const char*         readCString() const;
     String8             readString8() const;
+    status_t            readString8(String8* pArg) const;
     String16            readString16() const;
     status_t            readString16(String16* pArg) const;
     status_t            readString16(std::unique_ptr<String16>* pArg) const;