Add sparse array handling to Array.protoype.indexOf/lastIndexOf.

src/runtime.cc

 // Copyright 2006-2009 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 8181 matching lines @@
   Handle<Object> tmp2 = GetElement(jsobject, index2);
 
   SetElement(jsobject, index1, tmp2);
   SetElement(jsobject, index2, tmp1);
 
   return Heap::undefined_value();
 }
 
 
 // Returns an array that tells you where in the [0, length) interval an array
-// might have elements.  Can either return keys or intervals.  Keys can have
-// gaps in (undefined).  Intervals can also span over some undefined keys.
+// might have elements.  Can either return keys (positive integers) or
+// intervals (pair of a negative integer (-start-1) followed by a
+// positive (length)) or undefined values.
+// Intervals can span over some keys that are not in the object.
 static Object* Runtime_GetArrayKeys(Arguments args) {
   ASSERT(args.length() == 2);
   HandleScope scope;
   CONVERT_ARG_CHECKED(JSObject, array, 0);
   CONVERT_NUMBER_CHECKED(uint32_t, length, Uint32, args[1]);
   if (array->elements()->IsDictionary()) {
     // Create an array and get all the keys into it, then remove all the
     // keys that are not integers in the range 0 to length-1.
     Handle<FixedArray> keys = GetKeysInFixedArrayFor(array, INCLUDE_PROTOS);
     int keys_length = keys->length();
@@ skipping 2494 matching lines @@
   } else {
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     Counters::gc_last_resort_from_js.Increment();
     Heap::CollectAllGarbage(false);
   }
 }
 
 
 } }  // namespace v8::internal