add print to pdf for headless

headless/lib/browser/headless_devtools_manager_delegate.h

Index: headless/lib/browser/headless_devtools_manager_delegate.h
diff --git a/headless/lib/browser/headless_devtools_manager_delegate.h b/headless/lib/browser/headless_devtools_manager_delegate.h
index 6c2a65912567525a7e4dd173b3fb09b16898dec0..300cd2460080b721313de89470b085a6076d15cd 100644
--- a/headless/lib/browser/headless_devtools_manager_delegate.h
+++ b/headless/lib/browser/headless_devtools_manager_delegate.h
@@ -27,6 +27,9 @@ class HeadlessDevToolsManagerDelegate
   // DevToolsManagerDelegate implementation:
   base::DictionaryValue* HandleCommand(content::DevToolsAgentHost* agent_host,
                                        base::DictionaryValue* command) override;
+  bool HandleAsyncCommand(content::DevToolsAgentHost* agent_host,
+                          base::DictionaryValue* command,
+                          const CommandCallback& callback) override;
   scoped_refptr<content::DevToolsAgentHost> CreateNewTarget(
       const GURL& url) override;
   std::string GetDiscoveryPageHTML() override;
@@ -45,6 +48,10 @@ class HeadlessDevToolsManagerDelegate
   std::unique_ptr<base::DictionaryValue> DisposeBrowserContext(
       int command_id,
       const base::DictionaryValue* params);
+  void PrintToPDF(content::DevToolsAgentHost* agent_host,
+                  int command_id,
+                  const base::DictionaryValue* params,
+                  const CommandCallback& callback);
 
   base::WeakPtr<HeadlessBrowserImpl> browser_;
 
@@ -52,7 +59,13 @@ class HeadlessDevToolsManagerDelegate
       base::Callback<std::unique_ptr<base::DictionaryValue>(
           int command_id,
           const base::DictionaryValue* params)>;
+  using AsyncCommandMemberCallback =
+      base::Callback<void(content::DevToolsAgentHost* agent_host,
+                          int command_id,
+                          const base::DictionaryValue* params,
+                          const CommandCallback& callback)>;
   std::map<std::string, CommandMemberCallback> command_map_;
+  std::map<std::string, AsyncCommandMemberCallback> async_command_map_;
 };
 
 }  // namespace headless