Revert^4 "Lazily allocate DexCache arrays."

We rarely need the DexCache for compiled code.
Delay the allocation in hope we never need it.
This reduces DexCache memory usage by ~25% at startup.

Bug: b/181097963
Test: test.py -b --host
Change-Id: I1f654aeb538dfed013705a61b1955af1f6b94fe7
diff --git a/runtime/class_linker_test.cc b/runtime/class_linker_test.cc
index 035a9cb..e183146 100644
--- a/runtime/class_linker_test.cc
+++ b/runtime/class_linker_test.cc
@@ -1542,8 +1542,9 @@
                                                         nullptr,
                                                         nullptr));
   // Make a copy of the dex cache with changed name.
-  LinearAlloc* alloc = Runtime::Current()->GetLinearAlloc();
-  dex_cache.Assign(class_linker->AllocAndInitializeDexCache(Thread::Current(), *dex_file, alloc));
+  dex_cache.Assign(class_linker->AllocAndInitializeDexCache(Thread::Current(),
+                                                            *dex_file,
+                                                            /* class_loader= */ nullptr));
   DCHECK_EQ(dex_cache->GetLocation()->CompareTo(location.Get()), 0);
   {
     WriterMutexLock mu(soa.Self(), *Locks::dex_lock_);