[hydrogen] optimize switch with string clauses

src/type-info.cc

Index: src/type-info.cc
diff --git a/src/type-info.cc b/src/type-info.cc
index afec71a99a83d0ea7082712057f7e00f37a7e2c4..d522242e61b1fbd333c2d95954cf3f2e6f8ee285 100644
--- a/src/type-info.cc
+++ b/src/type-info.cc
@@ -360,6 +360,10 @@ TypeInfo TypeFeedbackOracle::SwitchType(CaseClause* clause) {
       return unknown;
     case CompareIC::SMIS:
       return TypeInfo::Smi();
+    case CompareIC::STRINGS:
+      return TypeInfo::String();
+    case CompareIC::SYMBOLS:
+      return TypeInfo::Symbol();
     case CompareIC::HEAP_NUMBERS:
       return TypeInfo::Number();
     case CompareIC::OBJECTS: