Bailout if field state changed during background compilation.

runtime/vm/intermediate_language_mips.cc

Index: runtime/vm/intermediate_language_mips.cc
diff --git a/runtime/vm/intermediate_language_mips.cc b/runtime/vm/intermediate_language_mips.cc
index 79736b9ca95932e755c077ea9b4fc3905afea8db..064bd6e1b768d3bf25ef966c71d06a44d8687eb4 100644
--- a/runtime/vm/intermediate_language_mips.cc
+++ b/runtime/vm/intermediate_language_mips.cc
@@ -7,6 +7,7 @@
 
 #include "vm/intermediate_language.h"
 
+#include "vm/compiler.h"
 #include "vm/dart_entry.h"
 #include "vm/flow_graph.h"
 #include "vm/flow_graph_compiler.h"
@@ -1614,6 +1615,10 @@ void GuardFieldClassInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   const intptr_t nullability = field().is_nullable() ? kNullCid : kIllegalCid;
 
   if (field_cid == kDynamicCid) {
+    if (Compiler::IsBackgroundCompilation()) {
+      // Field state changed while compiling.
+      Compiler::AbortBackgroundCompilation(deopt_id());
+    }
     ASSERT(!compiler->is_optimizing());
     return;  // Nothing to emit.
   }
@@ -1768,6 +1773,10 @@ LocationSummary* GuardFieldLengthInstr::MakeLocationSummary(Zone* zone,
 
 void GuardFieldLengthInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   if (field().guarded_list_length() == Field::kNoFixedLength) {
+    if (Compiler::IsBackgroundCompilation()) {
+      // Field state changed while compiling.
+      Compiler::AbortBackgroundCompilation(deopt_id());
+    }
     ASSERT(!compiler->is_optimizing());
     return;  // Nothing to emit.
   }