Revert "Revert "Support multiple DOM isolates and tweak devtools frontend to better handle large #s…

Source/bindings/core/dart/DartJsInterop.cpp

Index: Source/bindings/core/dart/DartJsInterop.cpp
diff --git a/Source/bindings/core/dart/DartJsInterop.cpp b/Source/bindings/core/dart/DartJsInterop.cpp
index 4b4e8f9900d55c8fc3cbf0ad5d1e42a4883949f1..4ac046c4c6680d2598e5e426486c68b22dc3f673 100644
--- a/Source/bindings/core/dart/DartJsInterop.cpp
+++ b/Source/bindings/core/dart/DartJsInterop.cpp
@@ -272,7 +272,12 @@ Dart_Handle JsInterop::toDart(v8::Local<v8::Value> v8Handle)
     if (DartHandleProxy::isDartProxy(v8Handle)) {
         DartPersistentValue* scriptValue = DartHandleProxy::readPointerFromProxy(v8Handle);
         ASSERT(scriptValue->isIsolateAlive());
-        return scriptValue->value();
+        // If the isolate does not match we fall back to using the existing JS
+        // wrapper for the Dart object so that simple cases that would work in
+        // Dart2Js work. We could alternately throw an exception here.
+        if (scriptValue->isolate() == Dart_CurrentIsolate()) {
+            return scriptValue->value();
+        }
     }
 
     return JsObject::toDart(object);