Fix shutdown crash in Sky

sky/engine/tonic/dart_state.cc

Index: sky/engine/tonic/dart_state.cc
diff --git a/sky/engine/tonic/dart_state.cc b/sky/engine/tonic/dart_state.cc
index c5bcdff71ebb2a3fd187fa3499c37d24724c37d3..a614d01e6404a3591093cb04c1ceda0a54c1adba 100644
--- a/sky/engine/tonic/dart_state.cc
+++ b/sky/engine/tonic/dart_state.cc
@@ -32,12 +32,16 @@ DartState::DartState()
 DartState::~DartState() {
 }
 
-void DartState::DidSetIsolateInternal() {
-  {
-    Scope dart_scope(this);
-    index_handle_.Set(this, ToDart("index"));
+void DartState::SetIsolate(Dart_Isolate isolate) {
+  CHECK(!isolate_);
+  isolate_ = isolate;
+  if (isolate_) {

[eseidel, 2015/06/10 19:56:41]

I might have early returned instead.  but ok.

+    {
+      Scope dart_scope(this);
+      index_handle_.Set(this, ToDart("index"));
+    }
+    DidSetIsolate();
   }
-  DidSetIsolate();
 }
 
 DartState* DartState::From(Dart_Isolate isolate) {