Add some v8 bindings files to GN build.

Source/bindings/modules/v8/custom/custom.gni

Index: Source/bindings/modules/v8/custom/custom.gni
diff --git a/Source/bindings/modules/v8/custom/custom.gni b/Source/bindings/modules/v8/custom/custom.gni
new file mode 100644
index 0000000000000000000000000000000000000000..561afef32c923b7e725d9d20fa75cceb13da7575
--- /dev/null
+++ b/Source/bindings/modules/v8/custom/custom.gni
@@ -0,0 +1,23 @@
+# Copyright 2014 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# Make the files absolute so they can be imported to anywhere.
+bindings_modules_v8_custom_files = get_path_info(
+  [
+    "V8AudioNodeCustom.cpp",
+    "V8ClientCustom.cpp",
+    "V8CryptoCustom.cpp",
+    "V8CryptoKeyCustom.cpp",
+    "V8CustomSQLStatementErrorCallback.cpp",
+    "V8DeviceMotionEventCustom.cpp",
+    "V8DeviceOrientationEventCustom.cpp",
+    "V8EntryCustom.cpp",
+    "V8EntrySyncCustom.cpp",
+    "V8SQLResultSetRowListCustom.cpp",
+    "V8SQLTransactionCustom.cpp",
+    "V8SQLTransactionSyncCustom.cpp",
+    "V8ServiceWorkerCustom.cpp",
+    "V8SubtleCryptoCustom.cpp",
+  ],
+  "abspath")