[turbofan] Add support for String.prototype.charCodeAt/charAt.

src/compiler/verifier.cc

Index: src/compiler/verifier.cc
diff --git a/src/compiler/verifier.cc b/src/compiler/verifier.cc
index 23adb7790bff05918c5520bc42bc875bdc82905d..100a2ff8f0b1b385af91608ab4c4b5078dca1c22 100644
--- a/src/compiler/verifier.cc
+++ b/src/compiler/verifier.cc
@@ -813,6 +813,12 @@ void Verifier::Visitor::Check(Node* node) {
       CheckValueInputIs(node, 1, Type::String());
       CheckUpperIs(node, Type::Boolean());
       break;
+    case IrOpcode::kStringCharCodeAt:
+      // (String, Unsigned32) -> UnsignedSmall
+      CheckValueInputIs(node, 0, Type::String());
+      CheckValueInputIs(node, 1, Type::Unsigned32());
+      CheckUpperIs(node, Type::UnsignedSmall());
+      break;
     case IrOpcode::kStringFromCharCode:
       // Number -> String
       CheckValueInputIs(node, 0, Type::Number());