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

content/public/browser/devtools_manager_delegate.cc

Index: content/public/browser/devtools_manager_delegate.cc
diff --git a/content/public/browser/devtools_manager_delegate.cc b/content/public/browser/devtools_manager_delegate.cc
index e4de444bdcf0d6941bfb28be0bb14968b4b41acc..da64ce91724a2b62a7d76b6d326dadb8f8d8f73a 100644
--- a/content/public/browser/devtools_manager_delegate.cc
+++ b/content/public/browser/devtools_manager_delegate.cc
@@ -23,9 +23,8 @@ std::string DevToolsManagerDelegate::GetTargetDescription(
   return std::string();
 }
 
-bool DevToolsManagerDelegate::DiscoverTargets(
-    const DevToolsAgentHost::DiscoveryCallback& callback) {
-  return false;
+DevToolsAgentHost::List DevToolsManagerDelegate::RemoteDebuggingTargets() {
+  return DevToolsAgentHost::GetOrCreateAll();
 }
 
 scoped_refptr<DevToolsAgentHost> DevToolsManagerDelegate::CreateNewTarget(