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

chrome/browser/extensions/api/identity/extension_token_key.h

Index: chrome/browser/extensions/api/identity/extension_token_key.h
diff --git a/chrome/browser/extensions/api/identity/extension_token_key.h b/chrome/browser/extensions/api/identity/extension_token_key.h
index b6a0f9fbf224a46b33a6cdc5d388856c081a1f2c..d722dee8a578b21998435ded139035894fca3454 100644
--- a/chrome/browser/extensions/api/identity/extension_token_key.h
+++ b/chrome/browser/extensions/api/identity/extension_token_key.h
@@ -14,6 +14,7 @@ struct ExtensionTokenKey {
   ExtensionTokenKey(const std::string& extension_id,
                     const std::string& account_id,
                     const std::set<std::string>& scopes);
+  ExtensionTokenKey(const ExtensionTokenKey& other);
   ~ExtensionTokenKey();
   bool operator<(const ExtensionTokenKey& rhs) const;
   std::string extension_id;