DevTools: allow embedder handling async remote debugger commands.

content/public/browser/devtools_manager_delegate.h

Index: content/public/browser/devtools_manager_delegate.h
diff --git a/content/public/browser/devtools_manager_delegate.h b/content/public/browser/devtools_manager_delegate.h
index ae1e2efe7f422acc5e786e556940bb58562751ca..69d2b06be4d429aa90838f6bb210452c54c1ab48 100644
--- a/content/public/browser/devtools_manager_delegate.h
+++ b/content/public/browser/devtools_manager_delegate.h
@@ -5,7 +5,9 @@
 #ifndef CONTENT_PUBLIC_BROWSER_DEVTOOLS_MANAGER_DELEGATE_H_
 #define CONTENT_PUBLIC_BROWSER_DEVTOOLS_MANAGER_DELEGATE_H_
 
+#include <memory>
 #include <string>
+
 #include "base/memory/ref_counted.h"
 #include "content/common/content_export.h"
 #include "content/public/browser/devtools_agent_host.h"
@@ -47,6 +49,11 @@ class CONTENT_EXPORT DevToolsManagerDelegate {
       DevToolsAgentHost* agent_host,
       base::DictionaryValue* command);
 
+  using CommandCallback =
+      base::Callback<void(std::unique_ptr<base::DictionaryValue> response)>;
+  virtual bool HandleAsyncCommand(DevToolsAgentHost* agent_host,
+                                  base::DictionaryValue* command,
+                                  CommandCallback callback);
   // Should return discovery page HTML that should list available tabs
   // and provide attach links.
   virtual std::string GetDiscoveryPageHTML();