Dispose external string resource on heap teardown.

test/cctest/test-api.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 17170 matching lines @@
   CHECK(string1->IsExternal());
   CHECK(string2->IsExternal());
   CHECK(string3->IsExternal());
 
   VisitorImpl visitor(resource);
   v8::V8::VisitExternalResources(&visitor);
   visitor.CheckVisitedResources();
 }
 
 
+TEST(ExternalStringCollectedAtTearDown) {
+  int destroyed = 0;
+  v8::Isolate* isolate = v8::Isolate::New();
+  { v8::Isolate::Scope isolate_scope(isolate);
+    v8::HandleScope handle_scope(isolate);
+    const char* s = "One string to test them all, one string to find them.";
+    TestAsciiResource* inscription =
+        new TestAsciiResource(i::StrDup(s), &destroyed);
+    v8::Local<v8::String> ring = v8::String::NewExternal(inscription);
+    // Ring is still alive.  Orcs are roaming freely across our lands.
+    CHECK_EQ(0, destroyed);
+    USE(ring);
+  }
+
+  isolate->Dispose();
+  // Ring has been destroyed.  Free Peoples of Middle-earth Rejoice.
+  CHECK_EQ(1, destroyed);
+}
+
+
 static double DoubleFromBits(uint64_t value) {
   double target;
   i::OS::MemCopy(&target, &value, sizeof(target));
   return target;
 }
 
 
 static uint64_t DoubleToBits(double value) {
   uint64_t target;
   i::OS::MemCopy(&target, &value, sizeof(target));
@@ skipping 3510 matching lines @@
   }
   for (int i = 0; i < runs; i++) {
     Local<String> expected;
     if (i != 0) {
       CHECK_EQ(v8_str("escape value"), values[i]);
     } else {
       CHECK(values[i].IsEmpty());
     }
   }
 }