Remove one more unneccessary conversion to double.

src/runtime.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 658 matching lines @@
 }
 
 
 bool Runtime::SetupArrayBuffer(Isolate* isolate,
                                Handle<JSArrayBuffer> array_buffer,
                                void* data,
                                size_t allocated_length) {
   array_buffer->set_backing_store(data);
 
   Handle<Object> byte_length =
-      isolate->factory()->NewNumber(static_cast<double>(allocated_length));
+      isolate->factory()->NewNumberFromSize(allocated_length);
   CHECK(byte_length->IsSmi() || byte_length->IsHeapNumber());
   array_buffer->set_byte_length(*byte_length);
   return true;
 }
 
 
 bool Runtime::SetupArrayBufferAllocatingData(
     Isolate* isolate,
     Handle<JSArrayBuffer> array_buffer,
     size_t allocated_length) {
@@ skipping 12805 matching lines @@
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     isolate->counters()->gc_last_resort_from_js()->Increment();
     isolate->heap()->CollectAllGarbage(Heap::kNoGCFlags,
                                        "Runtime::PerformGC");
   }
 }
 
 
 } }  // namespace v8::internal