Implement Blink-in-JS for DOM methods

Source/core/BUILD.gn

Index: Source/core/BUILD.gn
diff --git a/Source/core/BUILD.gn b/Source/core/BUILD.gn
index 08f3862b38e043b3c913a2e06b5174a24408e4ab..647234aea314be102b95706ee5b6638e2728db23 100644
--- a/Source/core/BUILD.gn
+++ b/Source/core/BUILD.gn
@@ -937,6 +937,9 @@ make_token_matcher("make_core_generated_make_token_matcher_for_viewport") {
 # One-off scripts --------------------------------------------------------------
 
 # "generatePrivateScript" in make_core_generated from GYP.
+# FIXME: The implementation of Blink-in-JS is not yet mature.
+# You can use Blink-in-JS in your local experiment, but don't ship it.
+# crbug.com/341031
 action("make_core_generated_private_script") {
   visibility = ":make_core_generated"
   script = "../build/scripts/make_private_script_source.py"
@@ -954,6 +957,23 @@ action("make_core_generated_private_script") {
   deps = make_core_generated_deps
 }
 
+action("make_core_generated_private_script_for_testing") {
+  visibility = ":make_core_generated"
+  script = "../build/scripts/make_private_script_source.py"
+
+  source_prereqs = [
+    "testing/Internals.js",
+  ]
+  outputs = [
+    "$blink_core_output_dir/PrivateScriptSourcesForTesting.h",
+  ]
+
+  args = rebase_path(outputs, root_build_dir)
+  args += rebase_path(source_prereqs, root_build_dir)
+
+  deps = make_core_generated_deps
+}
+
 # "generateXMLViewerCSS" in make_core_generated from GYP.
 action("make_core_generated_xml_viewer_css") {
   visibility = ":make_core_generated"