In code comments print also deopt reason for deoptimization stubs.

runtime/vm/flow_graph_compiler.h

Index: runtime/vm/flow_graph_compiler.h
===================================================================
--- runtime/vm/flow_graph_compiler.h	(revision 38465)
+++ runtime/vm/flow_graph_compiler.h	(working copy)
@@ -165,6 +165,16 @@
   // Implementation is in architecture specific file.
   virtual void GenerateCode(FlowGraphCompiler* compiler, intptr_t stub_ix);
 
+  const char* Name() const {
+    const char* kFormat = "Deopt stub for id %d, reason: %s";
+    const intptr_t len = OS::SNPrint(NULL, 0, kFormat,
+        deopt_id(), DeoptReasonToCString(reason())) + 1;
+    char* chars = Isolate::Current()->current_zone()->Alloc<char>(len);
+    OS::SNPrint(chars, len, kFormat,
+        deopt_id(), DeoptReasonToCString(reason()));
+    return chars;
+  }
+
  private:
   Label entry_label_;