Safepoint interface and unit tests.

runtime/vm/store_buffer.h

Index: runtime/vm/store_buffer.h
diff --git a/runtime/vm/store_buffer.h b/runtime/vm/store_buffer.h
index b8f36a5e369d70a791d07f16db9eccd25d048dfe..b1bd387e8fb87d8d657fd0a310adf5a94528ca57 100644
--- a/runtime/vm/store_buffer.h
+++ b/runtime/vm/store_buffer.h
@@ -97,6 +97,9 @@ class StoreBuffer {
   // Discards the contents of this store buffer.
   void Reset();
 
+  // Check whether non-empty blocks have exceeded kMaxNonEmpty.
+  bool Overflowed();
+
  private:
   class List {
    public:
@@ -113,10 +116,6 @@ class StoreBuffer {
     DISALLOW_COPY_AND_ASSIGN(List);
   };
 
-  // Check if we run over the max number of deduplication sets.
-  // If we did schedule an interrupt.
-  void CheckThresholdNonEmpty();
-
   // If needed, trims the the global cache of empty blocks.
   static void TrimGlobalEmpty();