Bug 1122835, Part 2: Simplify BitStringWithNoUnusedBits, r=keeler

--HG--
extra : rebase_source : 2beb4ceb866299454c3e9f5b93ac83a18c8fd1c2

security/pkix/lib/pkixder.cpp

@@ -319,9 +319,7 @@ BitStringWithNoUnusedBits(Reader& input, /*out*/ Input& value)
   if (unusedBitsAtEnd != 0) {
     return Result::ERROR_BAD_DER;
   }
-  Reader::Mark mark(valueWithUnusedBits.GetMark());
-  valueWithUnusedBits.SkipToEnd();
-  return valueWithUnusedBits.GetInput(mark, value);
+  return valueWithUnusedBits.SkipToEnd(value);
 }
 
 static inline Result