[d8] Fix use-external-strings flag.

BUG=v8:6093

Change-Id: I4572fcb4258c9a6ee6e5d5ed18e3567460c90211
Reviewed-on: https://chromium-review.googlesource.com/481300Reviewed-by: Daniel Vogelheim <vogelheim@chromium.org>
Reviewed-by: Marja Hölttä <marja@chromium.org>
Commit-Queue: Wiktor Garbacz <wiktorg@google.com>
Cr-Commit-Position: refs/heads/master@{#44723}

src/d8.cc

@@ -421,8 +421,6 @@ base::LazyMutex Shell::workers_mutex_;
 bool Shell::allow_new_workers_ = true;
 i::List<Worker*> Shell::workers_;
 std::vector<ExternalizedContents> Shell::externalized_contents_;
-std::vector<std::unique_ptr<String::ExternalOneByteStringResource>>
-    Shell::external_string_resources_;
 
 Global<Context> Shell::evaluation_context_;
 ArrayBuffer::Allocator* Shell::array_buffer_allocator;
@@ -2017,7 +2015,6 @@ Local<String> Shell::ReadFile(Isolate* isolate, const char* name) {
     String::ExternalOneByteStringResource* resource =
         new ExternalOwningOneByteStringResource(
             std::unique_ptr<const char[]>(chars), size);
-    external_string_resources_.emplace_back(resource);
     result = String::NewExternalOneByte(isolate, resource).ToLocalChecked();
   } else {
     result = String::NewFromUtf8(isolate, chars, NewStringType::kNormal, size)

src/d8.h

@@ -472,8 +472,6 @@ class Shell : public i::AllStatic {
   static bool allow_new_workers_;
   static i::List<Worker*> workers_;
   static std::vector<ExternalizedContents> externalized_contents_;
-  static std::vector<std::unique_ptr<v8::String::ExternalOneByteStringResource>>
-      external_string_resources_;
 
   static void WriteIgnitionDispatchCountersFile(v8::Isolate* isolate);
   // Append LCOV coverage data to file.