Fix rounding in Uint8ClampedArray setter.

src/platform.h

 // 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 53 matching lines @@
 // Windows specific stuff.
 #ifdef WIN32
 
 // Microsoft Visual C++ specific stuff.
 #ifdef _MSC_VER
 
 #include "win32-math.h"
 
 int strncasecmp(const char* s1, const char* s2, int n);
 
+inline int lrint(double flt) {
+  int intgr;
+#if defined(V8_TARGET_ARCH_IA32)
+  __asm {
+    fld flt
+    fistp intgr
+  };
+#else
+  intgr = static_cast<int>(flt + 0.5);
+  if ((intgr & 1) != 0 && intgr - flt == 0.5) {
+    // If the number is halfway between two integers, round to the even one.
+    intgr--;
+  }
+  return intgr;
+#endif
+}
+
+
 #endif  // _MSC_VER
 
 // Random is missing on both Visual Studio and MinGW.
 int random();
 
 #endif  // WIN32
 
 #include "atomicops.h"
 #include "lazy-instance.h"
 #include "platform-tls.h"
@@ skipping 675 matching lines @@
   Atomic32 active_;
   PlatformData* data_;  // Platform specific data.
   int samples_taken_;  // Counts stack samples taken.
   DISALLOW_IMPLICIT_CONSTRUCTORS(Sampler);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_PLATFORM_H_