IDL: Add build target for IDL dictionary impl generation in core

Source/bindings/core/v8/BUILD.gn

Index: Source/bindings/core/v8/BUILD.gn
diff --git a/Source/bindings/core/v8/BUILD.gn b/Source/bindings/core/v8/BUILD.gn
index 750a144af356cc553683165e09e594a75df62002..5a0e024984249c749e92bad9038b034c82f8f5ca 100644
--- a/Source/bindings/core/v8/BUILD.gn
+++ b/Source/bindings/core/v8/BUILD.gn
@@ -13,6 +13,7 @@ visibility = "//third_party/WebKit/Source/*"
 # bindings_core_v8_generated in core/v8/generated.gyp
 group("bindings_core_v8_generated") {
   deps = [
+    ":bindings_core_dictionary_impl_generated",
     ":bindings_core_v8_generated_aggregate",
     ":bindings_core_v8_generated_individual",
   ]
@@ -30,3 +31,11 @@ idl_compiler("bindings_core_v8_generated_individual") {
   sources = core_interface_idl_files
   output_dir = bindings_core_v8_output_dir
 }
+
+# bindings_core_dictionary_impl_generated in Source/bindings/core/v8/generated.gyp
+idl_dictionary("bindings_core_dictionary_impl_generated") {
+  # FIXME: Add 'core_dictionary_idl_files' to sources
+  sources = core_testing_dictionary_idl_files
+  # FIXME: Add 'generated_core_dictionary_files' to outputs
+  outputs = generated_core_testing_dictionary_files
+}