Array length reduction should throw in strict mode if it can't delete an element.

src/objects.h

 // Copyright 2015 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.
 
 #ifndef V8_OBJECTS_H_
 #define V8_OBJECTS_H_
 
 #include <iosfwd>
 
 #include "src/allocation.h"
@@ skipping 2048 matching lines @@
   // Returns the number of non-undefined values.
   static Handle<Object> PrepareElementsForSort(Handle<JSObject> object,
                                                uint32_t limit);
   // As PrepareElementsForSort, but only on objects where elements is
   // a dictionary, and it will stay a dictionary.  Collates undefined and
   // unexisting elements below limit from position zero of the elements.
   static Handle<Object> PrepareSlowElementsForSort(Handle<JSObject> object,
                                                    uint32_t limit);
 
   MUST_USE_RESULT static Maybe<bool> SetPropertyWithInterceptor(
-      LookupIterator* it, Handle<Object> value);
+      LookupIterator* it, ShouldThrow should_throw, Handle<Object> value);
 
   // SetLocalPropertyIgnoreAttributes converts callbacks to fields. We need to
   // grant an exemption to AccessorInfo callbacks in some cases.
   enum AccessorInfoHandling { DEFAULT_HANDLING, DONT_FORCE_FIELD };
 
   MUST_USE_RESULT static MaybeHandle<Object> DefineOwnPropertyIgnoreAttributes(
       LookupIterator* it, Handle<Object> value, PropertyAttributes attributes,
       AccessorInfoHandling handling = DEFAULT_HANDLING);
 
   MUST_USE_RESULT static Maybe<bool> DefineOwnPropertyIgnoreAttributes(
@@ skipping 430 matching lines @@
   MUST_USE_RESULT static Maybe<bool> SetPropertyWithFailedAccessCheck(
       LookupIterator* it, Handle<Object> value, ShouldThrow should_throw);
 
   // Add a property to a slow-case object.
   static void AddSlowProperty(Handle<JSObject> object,
                               Handle<Name> name,
                               Handle<Object> value,
                               PropertyAttributes attributes);
 
   MUST_USE_RESULT static Maybe<bool> DeletePropertyWithInterceptor(
-      LookupIterator* it);
+      LookupIterator* it, ShouldThrow should_throw);
 
   bool ReferencesObjectFromElements(FixedArray* elements,
                                     ElementsKind kind,
                                     Object* object);
 
   // Return the hash table backing store or the inline stored identity hash,
   // whatever is found.
   MUST_USE_RESULT Object* GetHiddenPropertiesHashTable();
 
   // Return the hash table backing store for hidden properties.  If there is no
@@ skipping 8252 matching lines @@
     }
     return value;
   }
 };
 
 
 }  // NOLINT, false-positive due to second-order macros.
 }  // NOLINT, false-positive due to second-order macros.
 
 #endif  // V8_OBJECTS_H_