gin: Add out-of-line copy ctors for complex classes.

This patch adds out of line copy constructors for classes that our
clang-plugin considers heavy. This is an effort to enable copy
constructor checks by default.

BUG=436357
[email protected], [email protected], [email protected]

Review URL: https://codereview.chromium.org/1727063002

Cr-Commit-Position: refs/heads/master@{#377655}
diff --git a/gin/object_template_builder.cc b/gin/object_template_builder.cc
index 158131f2..a40df60 100644
--- a/gin/object_template_builder.cc
+++ b/gin/object_template_builder.cc
@@ -145,6 +145,9 @@
   template_->SetInternalFieldCount(kNumberOfInternalFields);
 }
 
+ObjectTemplateBuilder::ObjectTemplateBuilder(
+    const ObjectTemplateBuilder& other) = default;
+
 ObjectTemplateBuilder::~ObjectTemplateBuilder() {
 }