Revert "Handle HCheckInstanceType and HIsStringAndBranch in check elimination."

src/unique.h

Index: src/unique.h
diff --git a/src/unique.h b/src/unique.h
index 8c7c47ed4fc0e3b76778226ba2dd359a73e6472b..8ed26829012c3980139d1a5d71c6d053e70eebe4 100644
--- a/src/unique.h
+++ b/src/unique.h
@@ -275,25 +275,6 @@ class UniqueSet V8_FINAL : public ZoneObject {
     return out;
   }
 
-  // Returns a new set representing all elements from this set which are not in
-  // that set. O(|this| * |that|).
-  UniqueSet<T>* Subtract(const UniqueSet<T>* that, Zone* zone) const {
-    if (that->size_ == 0) return this->Copy(zone);
-
-    UniqueSet<T>* out = new(zone) UniqueSet<T>(this->size_, zone);
-
-    int i = 0, j = 0;
-    while (i < this->size_) {
-      Unique<T> cand = this->array_[i];
-      if (!that->Contains(cand)) {
-        out->array_[j++] = cand;
-      }
-    }
-
-    out->size_ = j;
-    return out;
-  }
-
   // Makes an exact copy of this set. O(|this|).
   UniqueSet<T>* Copy(Zone* zone) const {
     UniqueSet<T>* copy = new(zone) UniqueSet<T>(this->size_, zone);