Refactor Thread lifecycle interface, add Thread::Enter/ExitIsolate.

runtime/include/dart_api.h

 /*
  * Copyright (c) 2012, 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 INCLUDE_DART_API_H_
 #define INCLUDE_DART_API_H_
 
 /** \mainpage Dart Embedding API Reference
@@ skipping 931 matching lines @@
  *
  * This name is unique to each isolate and should only be used to make
  * debugging messages more comprehensible.
  */
 DART_EXPORT Dart_Handle Dart_DebugName();
 
 /**
  * Enters an isolate. After calling this function,
  * the current isolate will be set to the provided isolate.
  *
- * Requires there to be no current isolate.
+ * Requires there to be no current isolate. Multiple threads may not be in
+ * the same isolate at once.
  */
 DART_EXPORT void Dart_EnterIsolate(Dart_Isolate isolate);
-/* TODO(turnidge): Describe what happens if two threads attempt to
- * enter the same isolate simultaneously. Check for this in the code.
- * Describe whether isolates are allowed to migrate. */
 
 /**
  * Notifies the VM that the current isolate is about to make a blocking call.
  */
 DART_EXPORT void Dart_IsolateBlocked();
 
 /**
  * Notifies the VM that the current isolate is no longer blocked.
  */
 DART_EXPORT void Dart_IsolateUnblocked();
@@ skipping 1856 matching lines @@
  * NOTE: If multiple callbacks with the same name are registered, only the
  * last callback registered will be remembered.
  */
 DART_EXPORT void Dart_RegisterRootServiceRequestCallback(
     const char* name,
     Dart_ServiceRequestCallback callback,
     void* user_data);
 
 
 #endif  /* INCLUDE_DART_API_H_ */  /* NOLINT */