VM: Fix race between background compiler and guarded cid update.

runtime/vm/isolate.h

Index: runtime/vm/isolate.h
diff --git a/runtime/vm/isolate.h b/runtime/vm/isolate.h
index b418fd6fec65f34c19cb88c74d6a6411a11fd56c..5c219ccb154c934041f5477051d9977863f5db82 100644
--- a/runtime/vm/isolate.h
+++ b/runtime/vm/isolate.h
@@ -560,14 +560,6 @@ class Isolate : public BaseIsolate {
 
   static const intptr_t kInvalidGen = 0;
 
-  void IncrFieldInvalidationGen() {
-    AtomicOperations::IncrementBy(&field_invalidation_gen_, 1);
-    if (field_invalidation_gen_ == kInvalidGen) {
-      AtomicOperations::IncrementBy(&field_invalidation_gen_, 1);
-    }
-  }
-  intptr_t field_invalidation_gen() const { return field_invalidation_gen_; }
-
   void IncrLoadingInvalidationGen() {
     AtomicOperations::IncrementBy(&loading_invalidation_gen_, 1);
     if (loading_invalidation_gen_ == kInvalidGen) {
@@ -578,14 +570,6 @@ class Isolate : public BaseIsolate {
     return AtomicOperations::LoadRelaxedIntPtr(&loading_invalidation_gen_);
   }
 
-  // Used by mutator thread to notify background compiler which fields
-  // triggered code invalidation.
-  void AddDisablingField(const Field& field);
-  // Returns Field::null() if none available in the list. Can be called
-  // only from background compiler and while mutator thread is at safepoint.
-  RawField* GetDisablingField();
-  void ClearDisablingFieldList();
-
   // Used by background compiler which field became boxed and must trigger
   // deoptimization in the mutator thread.
   void AddDeoptimizingBoxedField(const Field& field);
@@ -805,17 +789,13 @@ class Isolate : public BaseIsolate {
   // Invalidation generations; used to track events occuring in parallel
   // to background compilation. The counters may overflow, which is OK
   // since we check for equality to detect if an event occured.
-  intptr_t field_invalidation_gen_;
   intptr_t loading_invalidation_gen_;
   intptr_t top_level_parsing_count_;
 
-  // Protect access to boxed_field_list_ and disabling_field_list_.
+  // Protect access to boxed_field_list_.
   Mutex* field_list_mutex_;
   // List of fields that became boxed and that trigger deoptimization.
   RawGrowableObjectArray* boxed_field_list_;
-  // List of fields that were disabling code while background compiler
-  // was running.
-  RawGrowableObjectArray* disabling_field_list_;
 
   // This guards spawn_count_. An isolate cannot complete shutdown and be
   // destroyed while there are child isolates in the midst of a spawn.