Change heuristic to determine which fields contain modifieable double boxes: do it if field was ini…

runtime/vm/intermediate_language.h

Index: runtime/vm/intermediate_language.h
diff --git a/runtime/vm/intermediate_language.h b/runtime/vm/intermediate_language.h
index 44919ffa9451c45b08ed18efcbd1acac46d62809..9bae137f675b8bb06a79ebe4ef5f09ced9b1c211 100644
--- a/runtime/vm/intermediate_language.h
+++ b/runtime/vm/intermediate_language.h
@@ -335,6 +335,8 @@ class Value : public ZoneAllocated {
 
   void PrintTo(BufferFormatter* f) const;
 
+  const char* ToCString() const;
+
   const char* DebugName() const { return "Value"; }
 
   bool IsSmiValue() { return Type()->ToCid() == kSmiCid; }