Move StartIsolateScope into MessageHandler::HandleMessages

runtime/vm/isolate.h

 // Copyright (c) 2013, 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.
 
 #ifndef VM_ISOLATE_H_
 #define VM_ISOLATE_H_
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/base_isolate.h"
@@ skipping 744 matching lines @@
   DISALLOW_COPY_AND_ASSIGN(Isolate);
 };
 
 
 // When we need to execute code in an isolate, we use the
 // StartIsolateScope.
 class StartIsolateScope {
  public:
   explicit StartIsolateScope(Isolate* new_isolate)
       : new_isolate_(new_isolate), saved_isolate_(Isolate::Current()) {
-    ASSERT(new_isolate_ != NULL);
+    if (new_isolate_ == NULL) {
+      // Do nothing.
+      return;
+    }
     if (saved_isolate_ != new_isolate_) {
       ASSERT(Isolate::Current() == NULL);
       Isolate::SetCurrent(new_isolate_);
       new_isolate_->SetStackLimitFromStackBase(reinterpret_cast<uword>(this));
     }
   }
 
   ~StartIsolateScope() {
+    if (new_isolate_ == NULL) {
+      // Do nothing.
+      return;
+    }
     if (saved_isolate_ != new_isolate_) {
       new_isolate_->ClearStackLimit();
       Isolate::SetCurrent(saved_isolate_);
     }
   }
 
  private:
   Isolate* new_isolate_;
   Isolate* saved_isolate_;
 
@@ skipping 79 matching lines @@
   uint8_t* serialized_args_;
   intptr_t serialized_args_len_;
   uint8_t* serialized_message_;
   intptr_t serialized_message_len_;
   bool paused_;
 };
 
 }  // namespace dart
 
 #endif  // VM_ISOLATE_H_