Pull safe_conversions from chromium

Change-Id: I3d62b93d5a643c06626b34a8d69b09a7d50ec439
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2491382Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70745}

src/base/safe_conversions_impl.h

@@ -357,9 +357,17 @@ struct DstRangeRelationToSrcRangeImpl<
     using SrcLimits = std::numeric_limits<Src>;
     using DstLimits = NarrowingRange<Dst, Src, Bounds>;
     using Promotion = decltype(Src() + Dst());
+    bool ge_zero = false;
+    // Converting floating-point to integer will discard fractional part, so
+    // values in (-1.0, -0.0) will truncate to 0 and fit in Dst.
+    if (std::is_floating_point<Src>::value) {
+      ge_zero = value > Src(-1);
+    } else {
+      ge_zero = value >= Src(0);
+    }
     return RangeCheck(
-        value >= Src(0) && (DstLimits::lowest() == 0 ||
-                            static_cast<Dst>(value) >= DstLimits::lowest()),
+        ge_zero && (DstLimits::lowest() == 0 ||
+                    static_cast<Dst>(value) >= DstLimits::lowest()),
         static_cast<Promotion>(SrcLimits::max()) <=
                 static_cast<Promotion>(DstLimits::max()) ||
             static_cast<Promotion>(value) <=