Hide MirroredCompilationErrror behind a flag until post-1.0.

runtime/vm/exceptions.h

 // 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.
 
 #ifndef VM_EXCEPTIONS_H_
 #define VM_EXCEPTIONS_H_
 
 #include "vm/allocation.h"
 #include "vm/growable_array.h"
 
@@ skipping 40 matching lines @@
     kInternalError,
     kNullThrown,
     kIsolateSpawn,
     kIsolateUnhandledException,
     kJavascriptIntegerOverflowError,
     kAssertion,
     kCast,
     kType,
     kFallThrough,
     kAbstractClassInstantiation,
-    kMirroredUncaughtExceptionError,
     kMirroredCompilationError,
   };
 
   static void ThrowByType(ExceptionType type, const Array& arguments);
   static void ThrowOOM();
   static void ThrowStackOverflow();
   static void ThrowArgumentError(const Instance& arg);
 
   // Returns a RawInstance if the exception is successfully created,
   // otherwise returns a RawError.
   static RawObject* Create(ExceptionType type, const Array& arguments);
 
  private:
   DISALLOW_COPY_AND_ASSIGN(Exceptions);
 };
 
 }  // namespace dart
 
 #endif  // VM_EXCEPTIONS_H_