Introduce exception object and remove some uses of MaybeObject::IsFailure().

src/objects-debug.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 594 matching lines @@
   CHECK(IsOddball());
   Heap* heap = GetHeap();
   VerifyHeapPointer(to_string());
   Object* number = to_number();
   if (number->IsHeapObject()) {
     CHECK(number == heap->nan_value());
   } else {
     CHECK(number->IsSmi());
     int value = Smi::cast(number)->value();
     // Hidden oddballs have negative smis.
-    const int kLeastHiddenOddballNumber = -4;
+    const int kLeastHiddenOddballNumber = -5;
     CHECK_LE(value, 1);
     CHECK(value >= kLeastHiddenOddballNumber);
   }
   if (map() == heap->undefined_map()) {
     CHECK(this == heap->undefined_value());
   } else if (map() == heap->the_hole_map()) {
     CHECK(this == heap->the_hole_value());
   } else if (map() == heap->null_map()) {
     CHECK(this == heap->null_value());
   } else if (map() == heap->boolean_map()) {
     CHECK(this == heap->true_value() ||
           this == heap->false_value());
   } else if (map() == heap->uninitialized_map()) {
     CHECK(this == heap->uninitialized_value());
   } else if (map() == heap->no_interceptor_result_sentinel_map()) {
     CHECK(this == heap->no_interceptor_result_sentinel());
   } else if (map() == heap->arguments_marker_map()) {
     CHECK(this == heap->arguments_marker());
   } else if (map() == heap->termination_exception_map()) {
     CHECK(this == heap->termination_exception());
+  } else if (map() == heap->exception_map()) {
+    CHECK(this == heap->exception());
   } else {
     UNREACHABLE();
   }
 }
 
 
 void Cell::CellVerify() {
   CHECK(IsCell());
   VerifyObjectField(kValueOffset);
 }
@@ skipping 543 matching lines @@
   for (int i = 0; i < number_of_transitions(); ++i) {
     if (!CheckOneBackPointer(current_map, GetTarget(i))) return false;
   }
   return true;
 }
 
 
 #endif  // DEBUG
 
 } }  // namespace v8::internal