[vm] Remove Dart_MakeExternalString and --support-externalizable-strings

runtime/vm/intermediate_language.cc

Index: runtime/vm/intermediate_language.cc
diff --git a/runtime/vm/intermediate_language.cc b/runtime/vm/intermediate_language.cc
index 724e7db9c0903e50010da9b190face648604c3ab..38f0e08d32435e8e5d0280dcd1ee33b414242bb2 100644
--- a/runtime/vm/intermediate_language.cc
+++ b/runtime/vm/intermediate_language.cc
@@ -44,7 +44,6 @@ DEFINE_FLAG(bool,
             !USING_DBC,
             "Support unboxed double and float32x4 fields.");
 DECLARE_FLAG(bool, eliminate_type_checks);
-DECLARE_FLAG(bool, support_externalizable_strings);
 
 #if defined(DEBUG)
 void Instruction::CheckField(const Field& field) const {
@@ -148,18 +147,6 @@ static int OrderByFrequency(CidRange* const* a, CidRange* const* b) {
   return target_info_b->count - target_info_a->count;
 }
 
-bool Cids::ContainsExternalizableCids() const {
-  for (intptr_t i = 0; i < length(); i++) {
-    for (intptr_t cid = cid_ranges_[i]->cid_start;
-         cid <= cid_ranges_[i]->cid_end; cid++) {
-      if (Field::IsExternalizableCid(cid)) {
-        return true;
-      }
-    }
-  }
-  return false;
-}
-
 bool Cids::Equals(const Cids& other) const {
   if (length() != other.length()) return false;
   for (int i = 0; i < length(); i++) {
@@ -291,20 +278,6 @@ bool CheckClassInstr::AttributesEqual(Instruction* other) const {
   return cids().Equals(other_check->cids());
 }
 
-EffectSet CheckClassInstr::Dependencies() const {
-  // Externalization of strings via the API can change the class-id.
-  return cids_.ContainsExternalizableCids() ? EffectSet::Externalization()
-                                            : EffectSet::None();
-}
-
-EffectSet CheckClassIdInstr::Dependencies() const {
-  // Externalization of strings via the API can change the class-id.
-  for (intptr_t i = cids_.cid_start; i <= cids_.cid_end; i++) {
-    if (Field::IsExternalizableCid(i)) return EffectSet::Externalization();
-  }
-  return EffectSet::None();
-}
-
 bool CheckClassInstr::IsDeoptIfNull() const {
   if (!cids().IsMonomorphic()) {
     return false;