Revert "ART: Forbid the zygote to load code outside of system"

This reverts commit 9ef308da0ea8d1df2edf65d4957599fafcc56aeb.

Bug: 150032912
Bug: 129454856
Test: boots
Change-Id: I522b1e0e2b9116239ca206aa5c65347976eac7ab
diff --git a/runtime/oat_file_manager.cc b/runtime/oat_file_manager.cc
index 23e2ad2..3839dca 100644
--- a/runtime/oat_file_manager.cc
+++ b/runtime/oat_file_manager.cc
@@ -1037,9 +1037,9 @@
   }
 }
 
-void OatFileManager::SetOnlyUseSystemOatFiles(bool enforce, bool assert_no_files_loaded) {
+void OatFileManager::SetOnlyUseSystemOatFiles(bool assert_no_files_loaded) {
   ReaderMutexLock mu(Thread::Current(), *Locks::oat_file_manager_lock_);
-  if (!only_use_system_oat_files_ && enforce && assert_no_files_loaded) {
+  if (assert_no_files_loaded) {
     // Make sure all files that were loaded up to this point are on /system. Skip the image
     // files.
     std::vector<const OatFile*> boot_vector = GetBootOatFiles();
@@ -1051,7 +1051,7 @@
       }
     }
   }
-  only_use_system_oat_files_ = enforce;
+  only_use_system_oat_files_ = true;
 }
 
 void OatFileManager::DumpForSigQuit(std::ostream& os) {