Remove remaining uses of null's absolute address from non-IA32.

runtime/vm/assembler_mips.cc

Index: runtime/vm/assembler_mips.cc
diff --git a/runtime/vm/assembler_mips.cc b/runtime/vm/assembler_mips.cc
index 7823faf35a525172bb8c7c2f54aa07d57b6ec802..c08d4fa1886124e1846e13d15122a2f6d3bfa244 100644
--- a/runtime/vm/assembler_mips.cc
+++ b/runtime/vm/assembler_mips.cc
@@ -17,6 +17,7 @@ namespace dart {
 #if defined(USING_SIMULATOR)
 DECLARE_FLAG(int, trace_sim_after);
 #endif
+DECLARE_FLAG(bool, allow_absolute_addresses);
 DEFINE_FLAG(bool, print_stop_message, false, "Print stop message.");
 DECLARE_FLAG(bool, inline_alloc);
 
@@ -519,6 +520,7 @@ void Assembler::LoadObjectHelper(Register rd,
   if (object.IsSmi()) {
     LoadImmediate(rd, reinterpret_cast<int32_t>(object.raw()));
   } else if (object.InVMHeap() || !constant_pool_allowed()) {
+    ASSERT(FLAG_allow_absolute_addresses);
     // Make sure that class CallPattern is able to decode this load immediate.
     int32_t object_raw = reinterpret_cast<int32_t>(object.raw());
     const uint16_t object_low = Utils::Low16Bits(object_raw);
@@ -868,6 +870,7 @@ void Assembler::UpdateAllocationStats(intptr_t cid,
   intptr_t counter_offset =
       ClassTable::CounterOffsetFor(cid, space == Heap::kNew);
   if (inline_isolate) {
+    ASSERT(FLAG_allow_absolute_addresses);
     ClassTable* class_table = Isolate::Current()->class_table();
     ClassHeapStats** table_ptr = class_table->TableAddressFor(cid);
     if (cid < kNumPredefinedCids) {
@@ -946,6 +949,7 @@ void Assembler::MaybeTraceAllocation(intptr_t cid,
   ASSERT(temp_reg != TMP);
   intptr_t state_offset = ClassTable::StateOffsetFor(cid);
   if (inline_isolate) {
+    ASSERT(FLAG_allow_absolute_addresses);
     ClassTable* class_table = Isolate::Current()->class_table();
     ClassHeapStats** table_ptr = class_table->TableAddressFor(cid);
     if (cid < kNumPredefinedCids) {