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

chromecast/browser/devtools/cast_devtools_manager_delegate.cc

Index: chromecast/browser/devtools/cast_devtools_manager_delegate.cc
diff --git a/chromecast/browser/devtools/cast_devtools_manager_delegate.cc b/chromecast/browser/devtools/cast_devtools_manager_delegate.cc
index dbc44aacf7e6f7385457a59bec52eb76d8685548..dae84bd67282c2b72cfaae3d90f9e50b218c1629 100644
--- a/chromecast/browser/devtools/cast_devtools_manager_delegate.cc
+++ b/chromecast/browser/devtools/cast_devtools_manager_delegate.cc
@@ -33,15 +33,18 @@ CastDevToolsManagerDelegate::~CastDevToolsManagerDelegate() {
   g_devtools_manager_delegate = nullptr;
 }
 
-bool CastDevToolsManagerDelegate::DiscoverTargets(
-    const content::DevToolsAgentHost::DiscoveryCallback& callback) {
+bool CastDevToolsManagerDelegate::CanDiscoverTargets() {
+  return true;
+}
+
+content::DevToolsAgentHost::List
+CastDevToolsManagerDelegate::DiscoverTargets() {
   content::DevToolsAgentHost::List enabled_hosts;
   for (auto* web_contents : enabled_webcontents_) {
     enabled_hosts.push_back(
         content::DevToolsAgentHost::GetOrCreateFor(web_contents));
   }
-  callback.Run(enabled_hosts);
-  return true;
+  return enabled_hosts;
 }
 
 void CastDevToolsManagerDelegate::EnableWebContentsForDebugging(