Deoptimization can occur at Dart calls (includes native calls to C) but not at runtime calls. This …

runtime/vm/code_generator.h

Index: runtime/vm/code_generator.h
===================================================================
--- runtime/vm/code_generator.h	(revision 11533)
+++ runtime/vm/code_generator.h	(working copy)
@@ -80,6 +80,7 @@
   V(DeoptCheckClass)                                                           \
   V(DeoptCheckSmi)                                                             \
   V(DeoptAtCall)                                                               \
+  V(DeoptNumReasons)                                                           \
 
 enum DeoptReasonId {
 #define DEFINE_ENUM_LIST(name) k##name,
@@ -91,6 +92,8 @@
 RawCode* ResolveCompileInstanceCallTarget(Isolate* isolate,
                                           const Instance& receiver);
 
+void DeoptimizeAll();
+
 }  // namespace dart
 
 #endif  // VM_CODE_GENERATOR_H_