Fix crash in x64: handler's pc-offset must be in 32-bit uword range

runtime/vm/object.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 VM_OBJECT_H_
 #define VM_OBJECT_H_
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "platform/utils.h"
@@ skipping 3472 matching lines @@
   void SetBit(intptr_t bit_index, bool value) const;
 
   FINAL_HEAP_OBJECT_IMPLEMENTATION(Stackmap, Object);
   friend class BitmapBuilder;
   friend class Class;
 };
 
 
 class ExceptionHandlers : public Object {
  public:
+  static const intptr_t kInvalidPcOffset = 0;
+
   intptr_t num_entries() const;
 
   void GetHandlerInfo(intptr_t try_index,
                       RawExceptionHandlers::HandlerInfo* info) const;
 
   uword HandlerPCOffset(intptr_t try_index) const;
   intptr_t OuterTryIndex(intptr_t try_index) const;
   bool NeedsStacktrace(intptr_t try_index) const;
 
   void SetHandlerInfo(intptr_t try_index,
@@ skipping 4342 matching lines @@
 
 
 RawObject* MegamorphicCache::GetTargetFunction(const Array& array,
                                                intptr_t index) {
   return array.At((index * kEntryLength) + kTargetFunctionIndex);
 }
 
 }  // namespace dart
 
 #endif  // VM_OBJECT_H_