Speed up FastElementsAccessor::ValidContents by removing redundant handle scope.

src/elements.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/arguments.h"
 #include "src/conversions.h"
 #include "src/elements.h"
 #include "src/objects.h"
@@ skipping 973 matching lines @@
     Isolate* isolate = holder->GetIsolate();
     HandleScope scope(isolate);
     Handle<FixedArrayBase> elements(holder->elements(), isolate);
     Map* map = elements->map();
     DCHECK((IsFastSmiOrObjectElementsKind(KindTraits::Kind) &&
             (map == isolate->heap()->fixed_array_map() ||
              map == isolate->heap()->fixed_cow_array_map())) ||
            (IsFastDoubleElementsKind(KindTraits::Kind) ==
             ((map == isolate->heap()->fixed_array_map() && length == 0) ||
              map == isolate->heap()->fixed_double_array_map())));
+    if (length == 0) return;  // nothing to do!
     DisallowHeapAllocation no_gc;
+    Handle<BackingStore> backing_store = Handle<BackingStore>::cast(elements);
     for (int i = 0; i < length; i++) {
-      HandleScope scope(isolate);
-      Handle<BackingStore> backing_store = Handle<BackingStore>::cast(elements);
       DCHECK((!IsFastSmiElementsKind(KindTraits::Kind) ||
               BackingStore::get(backing_store, i)->IsSmi()) ||
              (IsFastHoleyElementsKind(KindTraits::Kind) ==
               backing_store->is_the_hole(i)));
     }
 #endif
   }
 };
 
 
@@ skipping 835 matching lines @@
       UNREACHABLE();
       break;
   }
 
   array->set_elements(*elms);
   array->set_length(Smi::FromInt(number_of_elements));
   return array;
 }
 
 } }  // namespace v8::internal