Move sticky_error_ from isolate to thread

runtime/vm/snapshot.cc

Index: runtime/vm/snapshot.cc
diff --git a/runtime/vm/snapshot.cc b/runtime/vm/snapshot.cc
index a1c1d5c259906da39be94c32abf7f1022efa013b..bbeef36c2a96bf5720fbf06ccfc9a2666848c1c6 100644
--- a/runtime/vm/snapshot.cc
+++ b/runtime/vm/snapshot.cc
@@ -234,8 +234,8 @@ RawObject* SnapshotReader::ReadObject() {
     return obj.raw();
   } else {
     // An error occurred while reading, return the error object.
-    const Error& err = Error::Handle(isolate()->object_store()->sticky_error());
-    isolate()->object_store()->clear_sticky_error();
+    const Error& err = Error::Handle(thread()->sticky_error());
+    thread()->clear_sticky_error();
     return err.raw();
   }
 }
@@ -2488,7 +2488,7 @@ intptr_t SnapshotWriter::FindVmSnapshotObject(RawObject* rawobj) {
 
 void SnapshotWriter::ThrowException(Exceptions::ExceptionType type,
                                     const char* msg) {
-  object_store()->clear_sticky_error();
+  thread()->clear_sticky_error();
   if (msg != NULL) {
     const String& msg_obj = String::Handle(String::New(msg));
     const Array& args = Array::Handle(Array::New(1));