Change custom NaN check to use isnan to fix pixel array

failures on ARM hardware.
Review URL: http://codereview.chromium.org/160269

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@2557 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/objects.cc

@@ -7060,20 +7060,16 @@ Object* PixelArray::SetValue(uint32_t index, Object* value) {
     if (value->IsSmi()) {
       int_value = Smi::cast(value)->value();
     } else if (value->IsHeapNumber()) {
-      static const DoubleRepresentation nan(OS::nan_value());
-      DoubleRepresentation double_value = HeapNumber::cast(value)->value();
-      if (nan.bits != double_value.bits) {
-        int_value = static_cast<int>(double_value.value + 0.5);
-      } else {
-        // NaN clamps to zero.
-        int_value = 0;
+      double double_value = HeapNumber::cast(value)->value();
+      if (!isnan(double_value)) {
+        // NaN clamps to zero (default). Other doubles are rounded to
+        // the nearest integer.
+        int_value = static_cast<int>(double_value + 0.5);
       }
-    } else if (value->IsUndefined()) {
-      int_value = 0;
     } else {
-      // All other types have been converted to a number type further up in the
-      // call chain.
-      UNREACHABLE();
+      // Clamp undefined to zero (default). All other types have been
+      // converted to a number type further up in the call chain.
+      ASSERT(value->IsUndefined());
     }
     if (int_value < 0) {
       clamped_value = 0;