Remove legacy restart code

runtime/vm/isolate_reload.cc

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/isolate_reload.h"
 
 #include "vm/become.h"
 #include "vm/bit_vector.h"
 #include "vm/code_generator.h"
 #include "vm/compiler.h"
@@ skipping 617 matching lines @@
     Dart_Handle retval = (I->library_tag_handler())(
         Dart_kScriptTag, Api::NewHandle(thread, packages_url.raw()),
         Api::NewHandle(thread, root_lib_url.raw()));
     result = Api::UnwrapHandle(retval);
   }
   //
   // WEIRD CONTROL FLOW ENDS.
   TIR_Print("---- EXITED TAG HANDLER\n");
 
   if (result.IsUnwindError()) {
-    // We can only propagate errors when there are Dart frames on the stack.
-    // TODO(johnmccutchan): Fix dartbug.com/29092.
     if (thread->top_exit_frame_info() == 0) {
-      FATAL(
-          "Got an Unwind Error in the middle of a reload. "
-          "http://dartbug.com/29092");
+      // We can only propagate errors when there are Dart frames on the stack.
+      // In this case there are no Dart frames on the stack and we set the
+      // thread's sticky error. This error will be returned to the message
+      // handler.
+      thread->set_sticky_error(Error::Cast(result));
+    } else {
+      // If the tag handler returns with an UnwindError error, propagate it and
+      // give up.
+      Exceptions::PropagateError(Error::Cast(result));
+      UNREACHABLE();
     }
-    // If the tag handler returns with an UnwindError error, propagate it and
-    // give up.
-    Exceptions::PropagateError(Error::Cast(result));
-    UNREACHABLE();
   }
 
   // Other errors (e.g. a parse error) are captured by the reload system.
   if (result.IsError()) {
     FinalizeFailedLoad(Error::Cast(result));
   }
 }
 
 
 void IsolateReloadContext::RegisterClass(const Class& new_cls) {
@@ skipping 1234 matching lines @@
         ASSERT(!super_cls.IsNull());
         super_cls.AddDirectSubclass(cls);
       }
     }
   }
 }
 
 #endif  // !PRODUCT
 
 }  // namespace dart