Fix rounding in Uint8ClampedArray setter.

src/objects.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 11610 matching lines @@
     } else if (value->IsHeapNumber()) {
       double double_value = HeapNumber::cast(value)->value();
       if (!(double_value > 0)) {
         // NaN and less than zero clamp to zero.
         clamped_value = 0;
       } else if (double_value > 255) {
         // Greater than 255 clamp to 255.
         clamped_value = 255;
       } else {
         // Other doubles are rounded to the nearest integer.
-        clamped_value = static_cast<uint8_t>(double_value + 0.5);
+        clamped_value = static_cast<uint8_t>(lrint(double_value));
       }
     } else {
       // Clamp undefined to zero (default). All other types have been
       // converted to a number type further up in the call chain.
       ASSERT(value->IsUndefined());
     }
     set(index, clamped_value);
   }
   return Smi::FromInt(clamped_value);
 }
@@ skipping 1525 matching lines @@
   set_year(Smi::FromInt(year), SKIP_WRITE_BARRIER);
   set_month(Smi::FromInt(month), SKIP_WRITE_BARRIER);
   set_day(Smi::FromInt(day), SKIP_WRITE_BARRIER);
   set_weekday(Smi::FromInt(weekday), SKIP_WRITE_BARRIER);
   set_hour(Smi::FromInt(hour), SKIP_WRITE_BARRIER);
   set_min(Smi::FromInt(min), SKIP_WRITE_BARRIER);
   set_sec(Smi::FromInt(sec), SKIP_WRITE_BARRIER);
 }
 
 } }  // namespace v8::internal