Update isolate documentation.

runtime/vm/exceptions.cc

 // Copyright (c) 2011, 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.
 
 #include "vm/exceptions.h"
 
 #include "vm/dart_api_impl.h"
 #include "vm/dart_entry.h"
 #include "vm/debugger.h"
 #include "vm/flags.h"
@@ skipping 652 matching lines @@
       class_name = &Symbols::UnsupportedError();
       break;
     case kInternalError:
       library = Library::CoreLibrary();
       class_name = &Symbols::InternalError();
       break;
     case kNullThrown:
       library = Library::CoreLibrary();
       class_name = &Symbols::NullThrownError();
       break;
+    case kIsolateMessage:
+      library = Library::IsolateLibrary();
+      class_name = &Symbols::IsolateMessageException();
+      break;
     case kIsolateSpawn:
       library = Library::IsolateLibrary();
       class_name = &Symbols::IsolateSpawnException();
       break;
     case kIsolateUnhandledException:
       library = Library::IsolateLibrary();
       class_name = &Symbols::IsolateUnhandledException();
       break;
     case kJavascriptIntegerOverflowError:
       library = Library::CoreLibrary();
@@ skipping 30 matching lines @@
       break;
   }
 
   return DartLibraryCalls::InstanceCreate(library,
                                           *class_name,
                                           *constructor_name,
                                           arguments);
 }
 
 }  // namespace dart