Fix Smi vs. HeapObject confusion in HConstants.

src/conversions.h

Index: src/conversions.h
diff --git a/src/conversions.h b/src/conversions.h
index c33de77cd1f45f83f3197557a03aaab6f7f84a40..1b76ac5b67606310acea32ccfb6120d58416b469 100644
--- a/src/conversions.h
+++ b/src/conversions.h
@@ -153,6 +153,12 @@ static inline bool IsMinusZero(double value) {
 }
 
 
+static inline bool IsSmiDouble(double value) {
+  return !IsMinusZero(value) && value >= Smi::kMinValue &&
+         value <= Smi::kMaxValue && value == FastI2D(FastD2I(value));
+}
+
+
 // Integer32 is an integer that can be represented as a signed 32-bit
 // integer. It has to be in the range [-2^31, 2^31 - 1].
 // We also have to check for negative 0 as it is not an Integer32.