Introduce new API to expose external string resource regardless of encoding.

test/cctest/test-api.cc

Index: test/cctest/test-api.cc
diff --git a/test/cctest/test-api.cc b/test/cctest/test-api.cc
index 4bd99a6d9e940abd97ba243ecb383a119f4854f3..09125e1407c1ae84921005737437dc74f79ddf0d 100644
--- a/test/cctest/test-api.cc
+++ b/test/cctest/test-api.cc
@@ -404,6 +404,10 @@ THREADED_TEST(ScriptUsingStringResource) {
     CHECK(source->IsExternal());
     CHECK_EQ(resource,
              static_cast<TestResource*>(source->GetExternalStringResource()));
+    String::Encoding encoding = String::UNKNOWN_ENCODING;
+    CHECK_EQ(static_cast<const String::ExternalStringResourceBase*>(resource),
+             source->GetExternalStringResourceBase(&encoding));
+    CHECK_EQ(String::TWO_BYTE_ENCODING, encoding);
     HEAP->CollectAllGarbage(i::Heap::kNoGCFlags);
     CHECK_EQ(0, dispose_count);
   }
@@ -419,9 +423,16 @@ THREADED_TEST(ScriptUsingAsciiStringResource) {
   {
     v8::HandleScope scope;
     LocalContext env;
-    Local<String> source =
-        String::NewExternal(new TestAsciiResource(i::StrDup(c_source),
-                                                  &dispose_count));
+    TestAsciiResource* resource = new TestAsciiResource(i::StrDup(c_source),
+                                                        &dispose_count);
+    Local<String> source = String::NewExternal(resource);
+    CHECK(source->IsExternalAscii());
+    CHECK_EQ(static_cast<const String::ExternalStringResourceBase*>(resource),
+             source->GetExternalAsciiStringResource());
+    String::Encoding encoding = String::UNKNOWN_ENCODING;
+    CHECK_EQ(static_cast<const String::ExternalStringResourceBase*>(resource),
+             source->GetExternalStringResourceBase(&encoding));
+    CHECK_EQ(String::ASCII_ENCODING, encoding);
     Local<Script> script = Script::Compile(source);
     Local<Value> value = script->Run();
     CHECK(value->IsNumber());
@@ -445,6 +456,11 @@ THREADED_TEST(ScriptMakingExternalString) {
     // Trigger GCs so that the newly allocated string moves to old gen.
     HEAP->CollectGarbage(i::NEW_SPACE);  // in survivor space now
     HEAP->CollectGarbage(i::NEW_SPACE);  // in old gen now
+    CHECK_EQ(source->IsExternal(), false);
+    CHECK_EQ(source->IsExternalAscii(), false);
+    String::Encoding encoding = String::UNKNOWN_ENCODING;
+    CHECK_EQ(NULL, source->GetExternalStringResourceBase(&encoding));
+    CHECK_EQ(String::ASCII_ENCODING, encoding);
     bool success = source->MakeExternal(new TestResource(two_byte_source,
                                                          &dispose_count));
     CHECK(success);