Implement flooring division by a constant via truncating division by a constant.

src/hydrogen-instructions.cc

Index: src/hydrogen-instructions.cc
diff --git a/src/hydrogen-instructions.cc b/src/hydrogen-instructions.cc
index b2f1708adec28fe4e915a0dc8d6baf310b938b5f..66ce9e1891e0f5c82d0b6bb0b4dd2cdf3c068792 100644
--- a/src/hydrogen-instructions.cc
+++ b/src/hydrogen-instructions.cc
@@ -1833,6 +1833,14 @@ Range* HMathFloorOfDiv::InferRange(Zone* zone) {
       ClearFlag(kLeftCanBeMinInt);
     }
 
+    if (!a->CanBeNegative()) {
+      ClearFlag(HValue::kLeftCanBeNegative);
+    }
+
+    if (!a->CanBePositive()) {
+      ClearFlag(HValue::kLeftCanBePositive);
+    }
+
     if (!a->Includes(kMinInt) || !b->Includes(-1)) {
       ClearFlag(kCanOverflow);
     }