construct gin::ObjectTemplateBuilder with an ObjectTemplate

This allows customizing the prototype of the constructed object.

Change-Id: Id302d6f3202468963f6659e6df64726bb6bdc9d7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2119183
Commit-Queue: Jeremy Apthorp <jeremya@chromium.org>
Reviewed-by: Jeremy Roman <jbroman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#753347}

gin/object_template_builder.cc

@@ -145,9 +145,14 @@ ObjectTemplateBuilder::ObjectTemplateBuilder(v8::Isolate* isolate)
 
 ObjectTemplateBuilder::ObjectTemplateBuilder(v8::Isolate* isolate,
                                              const char* type_name)
-    : isolate_(isolate),
-      type_name_(type_name),
-      template_(v8::ObjectTemplate::New(isolate)) {
+    : ObjectTemplateBuilder(isolate,
+                            type_name,
+                            v8::ObjectTemplate::New(isolate)) {}
+
+ObjectTemplateBuilder::ObjectTemplateBuilder(v8::Isolate* isolate,
+                                             const char* type_name,
+                                             v8::Local<v8::ObjectTemplate> tmpl)
+    : isolate_(isolate), type_name_(type_name), template_(tmpl) {
   template_->SetInternalFieldCount(kNumberOfInternalFields);
 }
 

gin/object_template_builder.h

@@ -46,6 +46,9 @@ class GIN_EXPORT ObjectTemplateBuilder {
  public:
   explicit ObjectTemplateBuilder(v8::Isolate* isolate);
   ObjectTemplateBuilder(v8::Isolate* isolate, const char* type_name);
+  ObjectTemplateBuilder(v8::Isolate* isolate,
+                        const char* type_name,
+                        v8::Local<v8::ObjectTemplate> tmpl);
   ObjectTemplateBuilder(const ObjectTemplateBuilder& other);
   ~ObjectTemplateBuilder();