VM restart + shutdown fixes

runtime/include/dart_api.h

Index: runtime/include/dart_api.h
diff --git a/runtime/include/dart_api.h b/runtime/include/dart_api.h
index ae9e1d20623b82f154ffaa17004c09cd2c9e17c2..c565895143f4917aa1ada80de7afee8c7542d106 100755
--- a/runtime/include/dart_api.h
+++ b/runtime/include/dart_api.h
@@ -131,7 +131,10 @@ typedef struct _Dart_Isolate* Dart_Isolate;
  *   occur in any function which triggers the execution of Dart code.
  *
  * - Fatal error handles are produced when the system wants to shut
- *   down the current isolate.
+ *   down the current isolate. Sometimes a fatal error may be a
+ *   restart request (see Dart_IsRestartRequest). If the embedder does
+ *   not support restarting the VM, then this should be treated as a
+ *   normal fatal error.
  *
  * --- Propagating errors ---
  *
@@ -268,6 +271,17 @@ DART_EXPORT bool Dart_IsCompilationError(Dart_Handle handle);
 DART_EXPORT bool Dart_IsFatalError(Dart_Handle handle);
 
 /**
+ * Is this error a request to restart the VM?
+ *
+ * If an embedder chooses to support restarting the VM from tools
+ * (such as a debugger), then this function is used to distinguish
+ * restart requests from other fatal errors.
+ *
+ * Requires there to be a current isolate.
+ */
+DART_EXPORT bool Dart_IsVMRestartRequest(Dart_Handle handle);
+
+/**
  * Gets the error message from an error handle.
  *
  * Requires there to be a current isolate.