[crankshaft] Ensure that we use inlined Array.prototype.shift only when there's no elements in the …

src/prototype.h

 // Copyright 2014 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_PROTOTYPE_H_
 #define V8_PROTOTYPE_H_
 
 #include "src/isolate.h"
 #include "src/objects.h"
 
@@ skipping 155 matching lines @@
     }
     MaybeHandle<Object> proto =
         JSProxy::GetPrototype(Handle<JSProxy>::cast(handle_));
     if (!proto.ToHandle(&handle_)) return false;
     is_at_end_ =
         where_to_end_ == END_AT_NON_HIDDEN || handle_->IsNull(isolate_);
     return true;
   }
 
   bool IsAtEnd() const { return is_at_end_; }
+  Isolate* isolate() const { return isolate_; }
 
  private:
   Isolate* isolate_;
   Object* object_;
   Handle<Object> handle_;
   WhereToEnd where_to_end_;
   bool is_at_end_;
   int seen_proxies_;
 
   DISALLOW_COPY_AND_ASSIGN(PrototypeIterator);
 };
 
 
 }  // namespace internal
 
 }  // namespace v8
 
 #endif  // V8_PROTOTYPE_H_