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

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index 5a6f4c2782f203e76b3e1d2b69397f1c197feaaf..109cff0873e6f45f4bcfe165013fd42f33d27db1 100644
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -624,6 +624,7 @@ class HValue : public ZoneObject {
     kCanBeDivByZero,
     kLeftCanBeMinInt,
     kLeftCanBeNegative,
+    kLeftCanBePositive,
     kAllowUndefinedAsNaN,
     kIsArguments,
     kTruncatingToInt32,
@@ -4105,6 +4106,8 @@ class HMathFloorOfDiv V8_FINAL : public HBinaryOperation {
     SetFlag(kCanOverflow);
     SetFlag(kCanBeDivByZero);
     SetFlag(kLeftCanBeMinInt);
+    SetFlag(kLeftCanBeNegative);
+    SetFlag(kLeftCanBePositive);
     SetFlag(kAllowUndefinedAsNaN);
   }