Fix bad reinterpret_cast of StringFromCodePointOperator

StringFromCodePointOperator needed to derive from Operator1<UnicodeEncoding>
rather than plain old Operator. This was thankfully caught by the CFI build.

R=bmeurer@chromium.org, caitp@chromium.org
BUG=v8:5498

Review-Url: https://codereview.chromium.org/2398403003
Cr-Commit-Position: refs/heads/master@{#40131}

src/compiler/simplified-operator.cc

@@ -474,10 +474,11 @@ struct SimplifiedOperatorGlobalCache final {
 #undef CHECKED
 
   template <UnicodeEncoding kEncoding>
-  struct StringFromCodePointOperator final : public Operator {
+  struct StringFromCodePointOperator final : public Operator1<UnicodeEncoding> {
     StringFromCodePointOperator()
-        : Operator(IrOpcode::kStringFromCodePoint, Operator::kPure,
-                   "StringFromCodePoint", 1, 0, 0, 1, 0, 0) {}
+        : Operator1<UnicodeEncoding>(IrOpcode::kStringFromCodePoint,
+                                     Operator::kPure, "StringFromCodePoint", 1,
+                                     0, 0, 1, 0, 0, kEncoding) {}
   };
   StringFromCodePointOperator<UnicodeEncoding::UTF16>
       kStringFromCodePointOperatorUTF16;