Revert "Hold dex caches live in class table"

This reverts commit d6d49e56c2b7b11f474acb80cb02bb1fe9b7861e.

Bug: 29083330

(cherry picked from commit f102faf1bcbdb2149e3e7bf27b1819f621b7894b)

Change-Id: Id0c921bd6fe422159f8daa598dc8e7c9ed6eca47
diff --git a/runtime/class_table.h b/runtime/class_table.h
index 854a85e..686381d 100644
--- a/runtime/class_table.h
+++ b/runtime/class_table.h
@@ -133,8 +133,8 @@
       REQUIRES(!lock_)
       SHARED_REQUIRES(Locks::mutator_lock_);
 
-  // Return true if we inserted the strong root, false if it already exists.
-  bool InsertStrongRoot(mirror::Object* obj)
+  // Return true if we inserted the dex file, false if it already exists.
+  bool InsertDexFile(mirror::Object* dex_file)
       REQUIRES(!lock_)
       SHARED_REQUIRES(Locks::mutator_lock_);
 
@@ -162,10 +162,9 @@
   mutable ReaderWriterMutex lock_;
   // We have a vector to help prevent dirty pages after the zygote forks by calling FreezeSnapshot.
   std::vector<ClassSet> classes_ GUARDED_BY(lock_);
-  // Extra strong roots that can be either dex files or dex caches. Dex files used by the class
-  // loader which may not be owned by the class loader must be held strongly live. Also dex caches
-  // are held live to prevent them being unloading once they have classes in them.
-  std::vector<GcRoot<mirror::Object>> strong_roots_ GUARDED_BY(lock_);
+  // Dex files used by the class loader which may not be owned by the class loader. We keep these
+  // live so that we do not have issues closing any of the dex files.
+  std::vector<GcRoot<mirror::Object>> dex_files_ GUARDED_BY(lock_);
 };
 
 }  // namespace art