Add read barrier support to the entrypoints.

Also remove "THIS_LOAD_REQUIRES_READ_BARRIER" since reading
an ArtMethod* no longer needs read barrier.

stub_test should also work with read barriers now.

Change-Id: I3fba18042de2f867a18dbdc38519986212bd9769
diff --git a/runtime/entrypoints_order_test.cc b/runtime/entrypoints_order_test.cc
index c05c935..f7a3cd5 100644
--- a/runtime/entrypoints_order_test.cc
+++ b/runtime/entrypoints_order_test.cc
@@ -311,8 +311,9 @@
                          sizeof(void*));
     EXPECT_OFFSET_DIFFNP(QuickEntryPoints, pNewStringFromStringBuilder, pReadBarrierJni,
                          sizeof(void*));
+    EXPECT_OFFSET_DIFFNP(QuickEntryPoints, pReadBarrierJni, pReadBarrierSlow, sizeof(void*));
 
-    CHECKED(OFFSETOF_MEMBER(QuickEntryPoints, pReadBarrierJni)
+    CHECKED(OFFSETOF_MEMBER(QuickEntryPoints, pReadBarrierSlow)
             + sizeof(void*) == sizeof(QuickEntryPoints), QuickEntryPoints_all);
   }
 };