DevTools: retain DTAH in all the targets to match their life time.

content/public/browser/devtools_agent_host.h

Index: content/public/browser/devtools_agent_host.h
diff --git a/content/public/browser/devtools_agent_host.h b/content/public/browser/devtools_agent_host.h
index 15fd91c3906b64fc510a4d4f2bc01a972cfdd3e7..1deed12873c4ff7d082cfe9bd3785d1025e53420 100644
--- a/content/public/browser/devtools_agent_host.h
+++ b/content/public/browser/devtools_agent_host.h
@@ -105,11 +105,6 @@ class CONTENT_EXPORT DevToolsAgentHost
   // Returns all DevToolsAgentHosts content is aware of.
   static List GetOrCreateAll();
 
-  using DiscoveryCallback = base::Callback<void(List)>;
-
-  // Returns all possible DevToolsAgentHosts embedder is aware of.
-  static void DiscoverAllHosts(const DiscoveryCallback& callback);
-
   // Starts remote debugging.
   // Takes ownership over |socket_factory|.
   // If |frontend_url| is empty, assumes it's bundled.