Revert "Revert "Add one LinearAlloc per ClassLoader""

Issue was fixed by:
https://android-review.googlesource.com/#/c/171945/

Bug: 22720414

This reverts commit 7de5dfe37f3cf24e1166412b589f6f67dcd1f1c0.
diff --git a/runtime/runtime.h b/runtime/runtime.h
index a35eac1..6154c34 100644
--- a/runtime/runtime.h
+++ b/runtime/runtime.h
@@ -570,6 +570,9 @@
   // Called from class linker.
   void SetSentinel(mirror::Object* sentinel) SHARED_REQUIRES(Locks::mutator_lock_);
 
+  // Create a normal LinearAlloc or low 4gb version if we are 64 bit AOT compiler.
+  LinearAlloc* CreateLinearAlloc();
+
  private:
   static void InitPlatformSignalHandlers();